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Estructura  de  hidrocarburos:Alcanos<br />
Clases de Hidrocarburos<br />
Hidrocarburos<br />Aromáticos<br />Alifáticos<br />
Hidrocarburos<br />Aromáticos<br />Alifáticos<br />Alcanos<br />Alquenos<br />Alquinos<br />
H<br />H<br />H<br />H<br />C<br />C<br />H<br />H<br />Hidrocarburos<br />	Los alcanos son hidrocarburos en los cualestod...
H<br />H<br />C<br />C<br />H<br />H<br />Hidrocarburos<br />	Los alquenos son hidrocarburosquecontienen un doble enlace c...
HC<br />CH<br />Hidrocarburos<br />	Los alquinos son hidrocarburosquecontienen un triple enlace carbono-carbono.<br />Alif...
H<br />H<br />H<br />H<br />H<br />H<br />Hidrocarburos<br />	Los hidrocarburosaromáticosmáscomúnes son los quecontienen u...
CnH2n+2<br />Introducción a los Alcanos:Metano, Etano y Propano<br />
Los Alcanosmás Simples<br />Metano	(CH4)  	CH4<br />Etano	(C2H6)	CH3CH3<br />Propano	(C3H8)	CH3CH2CH3<br />peb-160°C<br />...
Hibridación sp3 yEnlaces en el Metano<br />
Estructura del Metano<br />Tetrahédrica<br />ángulos de enlace  = 109.5°<br />longitud de enlace = 110 pm<br />sin embargo...
ConfiguraciónElectrónica del carbono<br />solo dos electronesdesapareados<br />debeformar enlaces con solo dos átomos de ...
Hibridación Orbital sp3<br />30´s  Linus Pauling<br />2p<br />Se promueve un electrón del orbital 2s al 2p<br />2s<br />
Hibridación Orbital sp3<br />2p<br />2p<br />2s<br />2s<br />
Hibridación Orbital sp3<br />2p<br />Mezclar (hibridizar) el orbital 2s y los tresorbitales 2p<br />2s<br />
Hibridación Orbital sp3<br />2p<br />2 sp3<br />4 orbitalessemillenosequivalentes son consistentes con cuatro enlaces y la...
Hibridación Orbital sp3<br />
PropiedadesNodales de los Orbitales<br />p<br />+<br />–<br />+<br />s<br />
Forma de los orbitaleshíbridossp3<br />p<br />+<br />–<br />Toma el orbital s y colócalo en la parte superior del orbital ...
+<br />Forma de los orbitaleshíbridos sp3<br />s + p<br />+<br />–<br />Complemento de ondaelectrónica en regionesdonde el...
–<br />híbridosp<br />+<br />el orbital mostradoeshíbridosp<br />procesoanalogousandotresorbitalesp y uno sdahíbridossp3<b...
+<br />–<br />híbridosp<br />- el orbital híbrido no essimétrico<br />- mayor probabilidad de encontrar un electrón en un ...
+<br />–<br />–<br />El enlace   C—H en el Metano<br />Traslape en fase de un orbital semilleno 1s de hidrógeno con un or...
Justificaciónpara la Hibridación Orbital <br />consistente con la estructura del metano<br />permite la formación de 4 enl...
Enlaces en el Etano<br />
Estructura del Etano<br />C2H6<br />CH3CH3<br />geometríatetrahédrica en cadacarbono<br />distancia de enlace C—H = 110 pm...
El enlace  C—C en el Etano<br />Traslape en fase de un orbital híbridosemillenosp3  de un carbono con un orbital híbridos...
El enlace  C—C en el Etano<br />Traslape en fase de un orbital híbridosemillenosp3  de un carbono con un orbital híbridos...
C4H10<br />Alcanos Isoméricos :Los Butanos<br />
n-Butano	CH3CH2CH2CH3<br />Isobutano	(CH3)3CH<br />bp -0.4°C<br />bp -10.2°C<br />
n-Alcanos Superiores<br />
CH3CH2CH2CH2CH3<br />n-Pentano<br />CH3CH2CH2CH2CH2CH3<br />n-Hexano<br />CH3CH2CH2CH2CH2CH2CH3<br />n-Heptano<br />
Los Isómeros C5H12<br />
C5H12<br />(CH3)2CHCH2CH3<br />CH3CH2CH2CH2CH3<br />Isopentano<br />n-Pentano<br />(CH3)4C<br />Neopentano<br />
¿Cuántosisómeros?<br />El número de isómeros se incrementa al incrementar el número de carbonos.<br />No hay unamanerasenc...
Tabla 1 Número de IsómerosConstitucionales de Alcanos<br />CH4	1	<br />C2H6	1<br />C3H8	1	<br />C4H10	2	<br />C5H12	3	<br ...
Tabla 1 Número de IsómerosConstitucionales de Alcanos<br />CH4	1	 C8H18	18<br />C2H6	1	 C9H20	35<br />C3H8	1	 C10H22	75<br...
Propiedades Físcas delos Alcanos y Cicloalcanos<br />
Boiling Points of Alkanes <br />	governed by strength of intermolecular attractive forces<br />alkanes are nonpolar, so di...
Induced dipole-Induced dipole attractive forces<br />+<br />–<br />+<br />–<br />	two nonpolar molecules<br />center of po...
Induced dipole-Induced dipole attractive forces<br />+<br />–<br />+<br />–<br />	movement of electrons creates an instant...
Induced dipole-Induced dipole attractive forces<br />–<br />+<br />–<br />+<br />	temporary dipole in one molecule (left) ...
Induced dipole-Induced dipole attractive forces<br />–<br />–<br />+<br />+<br />	temporary dipole in one molecule (left) ...
Induced dipole-Induced dipole attractive forces<br />–<br />–<br />+<br />+<br />	the result is a small attractive force b...
Induced dipole-Induced dipole attractive forces<br />–<br />–<br />+<br />+<br />	the result is a small attractive force b...
Boiling Points<br />increase with increasing number of carbons<br />	more atoms, more electrons, more 	opportunities for i...
Boiling Points<br />increase with increasing number of carbons<br />	more atoms, more electrons, more 	opportunities for i...
Boiling Points<br />decrease with chain branching<br />	branched molecules are more compact with	smaller surface area—fewe...
Propiedades Químicas:Combustión de Alcanos<br />All alkanes burn in air to givecarbon dioxide and water.<br />
Heats of Combustion<br />increase with increasing number of carbons<br />	more moles of O2 consumed, more moles	of CO2 and...
Heats of Combustion<br />Heptane<br />4817 kJ/mol<br />654 kJ/mol<br />Octane<br />5471 kJ/mol<br />654 kJ/mol<br />Nonane...
Heats of Combustion<br />increase with increasing number of carbons<br />	more moles of O2 consumed, more moles	of CO2 and...
5 kJ/mol<br />8 kJ/mol<br />6 kJ/mol<br />Heats of Combustion<br />5471 kJ/mol<br />5466 kJ/mol<br />5458 kJ/mol<br />5452...
Estructura  de Alquenos<br />
Alkenes<br />Alkenes are hydrocarbons that contain a carbon-carbon double bond<br />also called "olefins"<br />characteriz...
Hibridación sp2y Enlaces en el Etileno<br />
Structure of Ethylene<br />C2H4<br />H2C=CH2<br />planar<br />bond angles:  	close to 120°<br />bond distances: 	C—H = 110...
sp2 Orbital Hybridization<br />2p<br />Promote an electron from the 2s to the 2p orbital <br />2s<br />
sp2 Orbital Hybridization<br />2p<br />2p<br />2s<br />2s<br />
sp2 Orbital Hybridization<br />2p<br />Mix together (hybridize) the 2s orbital and two of the three 2p orbitals<br />2s<br />
sp2 Orbital Hybridization<br />2p<br />2 sp2<br />3 equivalent half-filled sp2 hybrid orbitals plus 1 p orbital left unhyb...
sp2 Orbital Hybridization<br />
<br /><br /><br /><br /><br />sp2 Orbital Hybridization<br />p<br />2 sp2<br />
 Bonding in Ethylene<br />the unhybridized p orbital of carbon is involved in  bondingto the other carbon <br />p<br />2...
 Bonding in Ethylene<br />
 Bonding in Ethylene<br />
Isomerismo en Alquenos<br />
Isomers<br />Isomers are different compounds thathave the same molecular formula.<br />
same connnectivity;different arrangementof atoms in space<br />different connectivity<br />Isomers <br />Constitutional is...
Isomers <br />Constitutional isomers<br />Stereoisomers<br />consider the isomeric alkenes of molecular formula C4H8<br />
H3C<br />H<br />CH2CH3<br />H<br />C<br />C<br />C<br />C<br />H3C<br />H<br />H<br />H<br />CH3<br />H3C<br />H<br />H3C<...
H3C<br />H<br />CH2CH3<br />H<br />C<br />C<br />C<br />C<br />H3C<br />H<br />H<br />H<br />CH3<br />H3C<br />C<br />C<br...
H3C<br />H<br />CH2CH3<br />H<br />C<br />C<br />C<br />C<br />H3C<br />H<br />H<br />H<br />H<br />H3C<br />C<br />C<br /...
CH3<br />H3C<br />H<br />H3C<br />C<br />C<br />C<br />C<br />H<br />H<br />H<br />CH3<br />Stereoisomers<br />trans-2-But...
Stereochemical Notation<br />	trans (identical or  	analogous substituents  	on opposite sides)<br />cis (identical or ana...
Figure<br />Interconversion of stereoisomericalkenes does not normally occur.Requires that component of doublebond be br...
Figure<br />cis<br />trans<br />
Naming Steroisomeric Alkenesby the E-Z Notational System<br />
C<br />C<br />Stereochemical Notation<br />CH2(CH2)6CO2H<br />CH3(CH2)6CH2<br />Oleic acid<br />H<br />H<br />	cis and tra...
Cl<br />Br<br />C<br />C<br />H<br />F<br />Example<br />What is needed:1)  	systematic body of rules for ranking   			sub...
C<br />C<br />The E-Z Notational System<br />E :	higher ranked substituents on opposite sides <br />Z :	higher ranked subs...
C<br />C<br />The E-Z Notational System<br />E :	higher ranked substituents on opposite sides <br />Z :	higher ranked subs...
higher<br />higher<br />C<br />C<br />C<br />C<br />lower<br />lower<br />Zusammen<br />The E-Z Notational System<br />E :...
C<br />C<br />C<br />C<br />The E-Z Notational System<br />Question:  How are substituents ranked?<br />Answer:  	They are...
The Cahn-Ingold-Prelog (CIP) System<br />	The system that we use was devised by	R. S. Cahn	Sir Christopher Ingold	Vladimir...
higher<br />higher<br />Br<br />Cl<br />C<br />C<br />F<br />H<br />lower<br />lower<br />Table   CIP Rules<br />(1)	Highe...
higher<br />higher<br />Br<br />Cl<br />C<br />C<br />F<br />H<br />lower<br />lower<br />Table   CIP Rules<br />(1)	Highe...
—C(H,H,H)<br />—C(C,H,H)<br />Table   CIP Rules<br />(2)  When two atoms are identical, compare the 	atoms attached to the...
Table   CIP Rules<br />(3)  Work outward from the point of attachment, 	comparing all the atoms attached to a 	particular ...
Table   CIP Rules<br />(4)  	Evaluate substituents one by one.  	Don't add atomic numbers within groups.<br />—CH2OH  outr...
Table   CIP Rules<br />(5)	An atom that is multiply bonded to another 	atom is considered to be replicated as a  	substitu...
Table   CIP Rules<br />	A table of commonly encountered  substituents ranked according to precedence is given on the insid...
Propiedades Físicas de Alquenos<br />
H<br />H<br />C<br />C<br />H<br />H<br />H3C<br />H<br />C<br />C<br />H<br />H<br /> = 0.3 D<br />Dipole moments<br />	...
 = 1.4 D<br />H<br />H<br />C<br />C<br />H<br />H<br />Cl<br />H<br />C<br />C<br />H<br />H<br />H3C<br />H<br />C<br /...
 = 1.4 D<br />H<br />H<br />C<br />C<br />Cl<br />H<br />H3C<br />H<br />C<br />C<br />Cl<br />H<br />H3C<br />H<br /> =...
 = 1.4 D<br />H<br />H<br />C<br />C<br />Cl<br />H<br />H3C<br />H<br />C<br />C<br />Cl<br />H<br />H3C<br />H<br />C<b...
R—C+<br />is more stable than<br />H—C+<br />•<br />R—C<br />is more stable than<br />•<br />H—C<br />R—C<br />is more sta...
Estabilidades Relativas de Alquenos<br />
H<br />R<br />C<br />C<br />H<br />H<br />H<br />R<br />C<br />C<br />C<br />C<br />C<br />C<br />R'<br />H<br />disubstit...
R"<br />R"<br />R<br />R<br />C<br />C<br />C<br />C<br />R'<br />H<br />R'<br />R"'<br />trisubstituted<br />tetrasubstit...
Substituent Effects on Alkene Stability<br />Electronic<br />disubstituted alkenes are more stable than monosubstituted al...
Figure  Heats of combustion of C4H8isomers.<br />2717 kJ/mol<br />+ 6O2<br />2710 kJ/mol<br />2707 kJ/mol<br />2700 kJ/mol...
Substituent Effects on Alkene Stability<br />Electronic<br />alkyl groups stabilize double bonds more than H<br />more hig...
H3C<br />CH3<br />C<br />C<br />H3C<br />CH3<br />Problem <br />Give the structure or make a molecular model of the most s...
Substituent Effects on Alkene Stability<br />Steric<br />trans alkenes are more stable than cis alkenes<br />cis alkenes a...
van der Waals straindue to crowding ofcis-methyl groups<br />Figure  cis and trans-2-Butene<br />cis-2-butene<br />trans-2...
Figure  cis and trans-2-Butene<br />van der Waals straindue to crowding ofcis-methyl groups<br />cis-2-butene<br />trans-2...
H3C<br />CH3<br />CH3<br />H3C<br />CH3<br />H3C<br />C<br />C<br />C<br />C<br />H<br />H<br />van der Waals Strain<br />...
Cicloalquenos<br />
Cycloalkenes<br />	Cyclopropene and cyclobutene have angle strain.<br />Larger cycloalkenes, such as cyclopenteneand cyclo...
H<br />H<br />H<br />H<br />Stereoisomeric cycloalkenes<br />cis-cyclooctene and trans-cycloocteneare stereoisomers<br />c...
H<br />H<br />Stereoisomeric cycloalkenes<br />trans-cyclooctene is smallest trans-cycloalkene  that is stable at room tem...
Stereoisomeric cycloalkenes<br />cis and trans-cyclododeceneare approximately equal instability<br />trans-Cyclododecene<b...
Structure and Bonding in Alkynes:sp Hybridization<br />
120 pm<br />H<br />C<br />C<br />H<br />106 pm<br />106 pm<br />121 pm<br />C<br />CH3<br />C<br />H<br />146 pm<br />106 ...
C<br />C<br />Cycloalkynes<br />Cyclononyne is the smallest cycloalkyne stable enough to be stored at room temperaturefor ...
Hibridación spy Enlaces en el Acetileno<br />
HC<br />CH<br />Structure of Acetylene<br />C2H2<br />linear<br />bond angles:  	180°<br />bond distances: 	C—H = 106 pm	C...
spOrbital Hybridization<br />2p<br />Promote an electron from the 2s to the 2p orbital <br />2s<br />
sp Orbital Hybridization<br />2p<br />2p<br />2s<br />2s<br />
spOrbital Hybridization<br />2p<br />Mix together (hybridize) the 2s orbital and one of the three 2p orbitals<br />2s<br />
sp Orbital Hybridization<br />2p<br />2 p<br />2 sp<br />2 equivalent half-filled sp hybrid orbitals plus 2 p orbitals lef...
sp Orbital Hybridization<br />
sp Orbital Hybridization<br /><br />2 p<br /><br />2 sp<br /><br />
 Bonding in Acetylene<br />the unhybridized p orbitals of carbon are involved in separate bonds to the other carbon <br ...
 Bonding in Acetylene<br />
 Bonding in Acetylene<br />
 Bonding in Acetylene<br />
H<br />C<br />C<br />Acidity of Acetyleneand Terminal Alkynes<br />
H2C<br />CH2<br />Acidity of Hydrocarbons<br />In general, hydrocarbons are     exceedingly weak acids<br />Compound	pKa<b...
HC<br />CH<br />H2C<br />CH2<br />Acetylene<br />Acetylene is a weak acid, but not nearlyas weak as alkanes or alkenes.<br...
pKa = 60<br />–<br />sp3<br />:<br />C<br />H++<br />H<br />C<br />H<br />sp2<br />:<br />pKa = 45<br />H++<br />C<br />C<...
NaC<br />CH<br />+<br />+<br />NaOH<br />NaC<br />H2O<br />CH<br />HC<br />CH<br />Sodium Acetylide<br />Objective:<br />	...
–<br />..<br />..<br />–<br />stronger acidpKa = 15.7<br />weaker acidpKa = 26<br />+<br />CH<br />C<br />:<br />+<br />CH...
+<br />+<br />NaNH2<br />NaC<br />NH3<br />CH<br />HC<br />CH<br />–<br />..<br />..<br />–<br />+<br />:<br />:<br />+<br...
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Estructura de__hidrocarburos

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Estructura de__hidrocarburos

  1. 1. Estructura de hidrocarburos:Alcanos<br />
  2. 2. Clases de Hidrocarburos<br />
  3. 3. Hidrocarburos<br />Aromáticos<br />Alifáticos<br />
  4. 4. Hidrocarburos<br />Aromáticos<br />Alifáticos<br />Alcanos<br />Alquenos<br />Alquinos<br />
  5. 5. H<br />H<br />H<br />H<br />C<br />C<br />H<br />H<br />Hidrocarburos<br /> Los alcanos son hidrocarburos en los cualestodos los enlaces son sencillos.<br />Alifáticos<br />Alcanos<br />
  6. 6. H<br />H<br />C<br />C<br />H<br />H<br />Hidrocarburos<br /> Los alquenos son hidrocarburosquecontienen un doble enlace carbono-carbono.<br />Alifáticos<br />Alquenos<br />
  7. 7. HC<br />CH<br />Hidrocarburos<br /> Los alquinos son hidrocarburosquecontienen un triple enlace carbono-carbono.<br />Alifáticos<br />Alquinos<br />
  8. 8. H<br />H<br />H<br />H<br />H<br />H<br />Hidrocarburos<br /> Los hidrocarburosaromáticosmáscomúnes son los quecontienen un anillo de benzeno.<br />Aromáticos<br />
  9. 9. CnH2n+2<br />Introducción a los Alcanos:Metano, Etano y Propano<br />
  10. 10. Los Alcanosmás Simples<br />Metano (CH4) CH4<br />Etano (C2H6) CH3CH3<br />Propano (C3H8) CH3CH2CH3<br />peb-160°C<br />peb-89°C<br />peb-42°C<br />
  11. 11. Hibridación sp3 yEnlaces en el Metano<br />
  12. 12. Estructura del Metano<br />Tetrahédrica<br />ángulos de enlace = 109.5°<br />longitud de enlace = 110 pm<br />sin embargo la estructurapareceinconsistentecon la configuraciónelectrónica del carbono<br />
  13. 13. ConfiguraciónElectrónica del carbono<br />solo dos electronesdesapareados<br />debeformar enlaces con solo dos átomos de hidrógeno<br />los enlaces debenestar en ángulo recto uno con respectoal otro<br />2p<br />2s<br />
  14. 14. Hibridación Orbital sp3<br />30´s Linus Pauling<br />2p<br />Se promueve un electrón del orbital 2s al 2p<br />2s<br />
  15. 15. Hibridación Orbital sp3<br />2p<br />2p<br />2s<br />2s<br />
  16. 16. Hibridación Orbital sp3<br />2p<br />Mezclar (hibridizar) el orbital 2s y los tresorbitales 2p<br />2s<br />
  17. 17. Hibridación Orbital sp3<br />2p<br />2 sp3<br />4 orbitalessemillenosequivalentes son consistentes con cuatro enlaces y la geometríatetrahédrica<br />2s<br />
  18. 18. Hibridación Orbital sp3<br />
  19. 19. PropiedadesNodales de los Orbitales<br />p<br />+<br />–<br />+<br />s<br />
  20. 20. Forma de los orbitaleshíbridossp3<br />p<br />+<br />–<br />Toma el orbital s y colócalo en la parte superior del orbital p<br />+<br />s<br />
  21. 21. +<br />Forma de los orbitaleshíbridos sp3<br />s + p<br />+<br />–<br />Complemento de ondaelectrónica en regionesdonde el signoes el mismo<br />Interferenciadestructiva en regiones de signoopuesto<br />
  22. 22. –<br />híbridosp<br />+<br />el orbital mostradoeshíbridosp<br />procesoanalogousandotresorbitalesp y uno sdahíbridossp3<br />la forma de los híbridossp3es similar<br />Forma de los orbitaleshíbridossp3<br />
  23. 23. +<br />–<br />híbridosp<br />- el orbital híbrido no essimétrico<br />- mayor probabilidad de encontrar un electrón en un lado del núcleoque en otro<br />- produce enlaces másfuertes<br />Forma de los orbitaleshíbridossp3<br />
  24. 24. +<br />–<br />–<br />El enlace  C—H en el Metano<br />Traslape en fase de un orbital semilleno 1s de hidrógeno con un orbital híbridosemillenosp3 de carbono: <br />+<br />sp3<br />s<br />H<br />C<br />produce un enlace  .<br />+<br />H—C <br />C<br />H<br />
  25. 25. Justificaciónpara la Hibridación Orbital <br />consistente con la estructura del metano<br />permite la formación de 4 enlaces en lugar de 2<br />los enlaces involucrados en los orbitaleshíbridossp3 son másfuertesque los involucrados en el traslapes-s o p-p<br />
  26. 26. Enlaces en el Etano<br />
  27. 27. Estructura del Etano<br />C2H6<br />CH3CH3<br />geometríatetrahédrica en cadacarbono<br />distancia de enlace C—H = 110 pm<br />distancia de enlace C—C = 153 pm<br />
  28. 28. El enlace  C—C en el Etano<br />Traslape en fase de un orbital híbridosemillenosp3 de un carbono con un orbital híbridosemillenosp3de otro.<br /> El traslapees a lo largo del ejeinternuclearparadar un enlace .<br />
  29. 29. El enlace  C—C en el Etano<br />Traslape en fase de un orbital híbridosemillenosp3 de un carbono con un orbital híbridosemillenosp3de otro.<br /> El traslapees a lo largo del ejeinternuclearparadar un enlace .<br />
  30. 30. C4H10<br />Alcanos Isoméricos :Los Butanos<br />
  31. 31. n-Butano CH3CH2CH2CH3<br />Isobutano (CH3)3CH<br />bp -0.4°C<br />bp -10.2°C<br />
  32. 32. n-Alcanos Superiores<br />
  33. 33. CH3CH2CH2CH2CH3<br />n-Pentano<br />CH3CH2CH2CH2CH2CH3<br />n-Hexano<br />CH3CH2CH2CH2CH2CH2CH3<br />n-Heptano<br />
  34. 34. Los Isómeros C5H12<br />
  35. 35. C5H12<br />(CH3)2CHCH2CH3<br />CH3CH2CH2CH2CH3<br />Isopentano<br />n-Pentano<br />(CH3)4C<br />Neopentano<br />
  36. 36. ¿Cuántosisómeros?<br />El número de isómeros se incrementa al incrementar el número de carbonos.<br />No hay unamanerasencilla de predecircuántosisómeros hay paraunafórmula molecular en particular.<br />
  37. 37. Tabla 1 Número de IsómerosConstitucionales de Alcanos<br />CH4 1 <br />C2H6 1<br />C3H8 1 <br />C4H10 2 <br />C5H12 3 <br />C6H14 5 <br />C7H16 9 <br />
  38. 38. Tabla 1 Número de IsómerosConstitucionales de Alcanos<br />CH4 1 C8H18 18<br />C2H6 1 C9H20 35<br />C3H8 1 C10H22 75<br />C4H10 2 C15H32 4,347<br />C5H12 3 C20H42 366,319<br />C6H14 5 C40H82 62,491,178,805,831<br />C7H16 9 <br />
  39. 39. Propiedades Físcas delos Alcanos y Cicloalcanos<br />
  40. 40. Boiling Points of Alkanes <br /> governed by strength of intermolecular attractive forces<br />alkanes are nonpolar, so dipole-dipole and dipole-induced dipole forces are absent<br />only forces of intermolecular attraction are induced dipole-induced dipole forces<br />
  41. 41. Induced dipole-Induced dipole attractive forces<br />+<br />–<br />+<br />–<br /> two nonpolar molecules<br />center of positive charge and center of negative charge coincide in each<br />
  42. 42. Induced dipole-Induced dipole attractive forces<br />+<br />–<br />+<br />–<br /> movement of electrons creates an instantaneous dipole in one molecule (left)<br />
  43. 43. Induced dipole-Induced dipole attractive forces<br />–<br />+<br />–<br />+<br /> temporary dipole in one molecule (left) induces a complementary dipole in other molecule (right)<br />
  44. 44. Induced dipole-Induced dipole attractive forces<br />–<br />–<br />+<br />+<br /> temporary dipole in one molecule (left) induces a complementary dipole in other molecule (right)<br />
  45. 45. Induced dipole-Induced dipole attractive forces<br />–<br />–<br />+<br />+<br /> the result is a small attractive force between the two molecules<br />
  46. 46. Induced dipole-Induced dipole attractive forces<br />–<br />–<br />+<br />+<br /> the result is a small attractive force between the two molecules<br />
  47. 47. Boiling Points<br />increase with increasing number of carbons<br /> more atoms, more electrons, more opportunities for induced dipole-induced dipole forces <br />decrease with chain branching<br /> branched molecules are more compact with smaller surface area—fewer points of contact with other molecules <br />
  48. 48. Boiling Points<br />increase with increasing number of carbons<br /> more atoms, more electrons, more opportunities for induced dipole-induced dipole forces <br />Heptanebp 98°C<br />Octanebp 125°C<br />Nonanebp 150°C<br />
  49. 49. Boiling Points<br />decrease with chain branching<br /> branched molecules are more compact with smaller surface area—fewer points of contact with other molecules <br />Octane: bp 125°C<br />2-Methylheptane: bp 118°C<br />2,2,3,3-Tetramethylbutane: bp 107°C<br />
  50. 50. Propiedades Químicas:Combustión de Alcanos<br />All alkanes burn in air to givecarbon dioxide and water.<br />
  51. 51. Heats of Combustion<br />increase with increasing number of carbons<br /> more moles of O2 consumed, more moles of CO2 and H2O formed<br />
  52. 52. Heats of Combustion<br />Heptane<br />4817 kJ/mol<br />654 kJ/mol<br />Octane<br />5471 kJ/mol<br />654 kJ/mol<br />Nonane<br />6125 kJ/mol<br />
  53. 53. Heats of Combustion<br />increase with increasing number of carbons<br /> more moles of O2 consumed, more moles of CO2 and H2O formed<br />decrease with chain branching<br /> branched molecules are more stable (have less potential energy) than their unbranched isomers<br />
  54. 54. 5 kJ/mol<br />8 kJ/mol<br />6 kJ/mol<br />Heats of Combustion<br />5471 kJ/mol<br />5466 kJ/mol<br />5458 kJ/mol<br />5452 kJ/mol<br />
  55. 55. Estructura de Alquenos<br />
  56. 56. Alkenes<br />Alkenes are hydrocarbons that contain a carbon-carbon double bond<br />also called "olefins"<br />characterized by molecular formula CnH2n<br />said to be "unsaturated"<br />
  57. 57. Hibridación sp2y Enlaces en el Etileno<br />
  58. 58. Structure of Ethylene<br />C2H4<br />H2C=CH2<br />planar<br />bond angles: close to 120°<br />bond distances: C—H = 110 pm C=C = 134 pm<br />
  59. 59. sp2 Orbital Hybridization<br />2p<br />Promote an electron from the 2s to the 2p orbital <br />2s<br />
  60. 60. sp2 Orbital Hybridization<br />2p<br />2p<br />2s<br />2s<br />
  61. 61. sp2 Orbital Hybridization<br />2p<br />Mix together (hybridize) the 2s orbital and two of the three 2p orbitals<br />2s<br />
  62. 62. sp2 Orbital Hybridization<br />2p<br />2 sp2<br />3 equivalent half-filled sp2 hybrid orbitals plus 1 p orbital left unhybridized<br />2s<br />
  63. 63. sp2 Orbital Hybridization<br />
  64. 64. <br /><br /><br /><br /><br />sp2 Orbital Hybridization<br />p<br />2 sp2<br />
  65. 65.  Bonding in Ethylene<br />the unhybridized p orbital of carbon is involved in  bondingto the other carbon <br />p<br />2 sp2<br />
  66. 66.  Bonding in Ethylene<br />
  67. 67.  Bonding in Ethylene<br />
  68. 68. Isomerismo en Alquenos<br />
  69. 69. Isomers<br />Isomers are different compounds thathave the same molecular formula.<br />
  70. 70. same connnectivity;different arrangementof atoms in space<br />different connectivity<br />Isomers <br />Constitutional isomers<br />Stereoisomers<br />
  71. 71. Isomers <br />Constitutional isomers<br />Stereoisomers<br />consider the isomeric alkenes of molecular formula C4H8<br />
  72. 72. H3C<br />H<br />CH2CH3<br />H<br />C<br />C<br />C<br />C<br />H3C<br />H<br />H<br />H<br />CH3<br />H3C<br />H<br />H3C<br />C<br />C<br />C<br />C<br />H<br />H<br />H<br />CH3<br />1-Butene<br />2-Methylpropene<br />trans-2-Butene<br />cis-2-Butene<br />
  73. 73. H3C<br />H<br />CH2CH3<br />H<br />C<br />C<br />C<br />C<br />H3C<br />H<br />H<br />H<br />CH3<br />H3C<br />C<br />C<br />H<br />H<br />1-Butene<br />2-Methylpropene<br />Constitutional isomers<br />cis-2-Butene<br />
  74. 74. H3C<br />H<br />CH2CH3<br />H<br />C<br />C<br />C<br />C<br />H3C<br />H<br />H<br />H<br />H<br />H3C<br />C<br />C<br />H<br />CH3<br />1-Butene<br />2-Methylpropene<br />Constitutional isomers<br />trans-2-Butene<br />
  75. 75. CH3<br />H3C<br />H<br />H3C<br />C<br />C<br />C<br />C<br />H<br />H<br />H<br />CH3<br />Stereoisomers<br />trans-2-Butene<br />cis-2-Butene<br />
  76. 76. Stereochemical Notation<br /> trans (identical or analogous substituents on opposite sides)<br />cis (identical or analogous substitutents on same side)<br />
  77. 77. Figure<br />Interconversion of stereoisomericalkenes does not normally occur.Requires that component of doublebond be broken.<br />cis<br />trans<br />
  78. 78. Figure<br />cis<br />trans<br />
  79. 79. Naming Steroisomeric Alkenesby the E-Z Notational System<br />
  80. 80. C<br />C<br />Stereochemical Notation<br />CH2(CH2)6CO2H<br />CH3(CH2)6CH2<br />Oleic acid<br />H<br />H<br /> cis and trans are useful when substituents are identical or analogous (oleic acid has a cis double bond)<br />cis and trans are ambiguous when analogies are not obvious<br />
  81. 81. Cl<br />Br<br />C<br />C<br />H<br />F<br />Example<br />What is needed:1) systematic body of rules for ranking substituents<br /> 2) new set of stereochemical symbols other than cis and trans<br />
  82. 82. C<br />C<br />The E-Z Notational System<br />E : higher ranked substituents on opposite sides <br />Z : higher ranked substituents on same side <br />higher<br />lower<br />
  83. 83. C<br />C<br />The E-Z Notational System<br />E : higher ranked substituents on opposite sides <br />Z : higher ranked substituents on same side <br />lower<br />higher<br />
  84. 84. higher<br />higher<br />C<br />C<br />C<br />C<br />lower<br />lower<br />Zusammen<br />The E-Z Notational System<br />E : higher ranked substituents on opposite sides <br />Z : higher ranked substituents on same side <br />higher<br />lower<br />higher<br />lower<br />Entgegen<br />
  85. 85. C<br />C<br />C<br />C<br />The E-Z Notational System<br />Question: How are substituents ranked?<br />Answer: They are ranked in order of decreasing atomic number.<br />higher<br />lower<br />higher<br />higher<br />higher<br />lower<br />lower<br />lower<br />Entgegen<br />Zusammen<br />
  86. 86. The Cahn-Ingold-Prelog (CIP) System<br /> The system that we use was devised by R. S. Cahn Sir Christopher Ingold Vladimir Prelog<br /> Their rules for ranking groups were devised in connection with a different kind of stereochemistry—one that we will discuss later—but have been adapted to alkene stereochemistry.<br />
  87. 87. higher<br />higher<br />Br<br />Cl<br />C<br />C<br />F<br />H<br />lower<br />lower<br />Table CIP Rules<br />(1) Higher atomic number outranks lower atomic number<br />Br > F Cl > H<br />
  88. 88. higher<br />higher<br />Br<br />Cl<br />C<br />C<br />F<br />H<br />lower<br />lower<br />Table CIP Rules<br />(1) Higher atomic number outranks lower atomic number<br />Br > F Cl > H<br />(Z )-1-Bromo-2-chloro-1-fluoroethene<br />
  89. 89. —C(H,H,H)<br />—C(C,H,H)<br />Table CIP Rules<br />(2) When two atoms are identical, compare the atoms attached to them on the basis of their atomic numbers. Precedence is established at the first point of difference. <br />—CH2CH3 outranks —CH3<br />
  90. 90. Table CIP Rules<br />(3) Work outward from the point of attachment, comparing all the atoms attached to a particular atom before proceeding further along the chain. <br />—CH(CH3)2 outranks —CH2CH2OH<br />—C(C,H,H)<br />—C(C,C,H)<br />
  91. 91. Table CIP Rules<br />(4) Evaluate substituents one by one. Don't add atomic numbers within groups.<br />—CH2OH outranks —C(CH3)3<br />—C(O,H,H)<br />—C(C,C,C)<br />
  92. 92. Table CIP Rules<br />(5) An atom that is multiply bonded to another atom is considered to be replicated as a substituent on that atom.<br />—CH=O outranks —CH2OH<br />—C(O,O,H)<br />—C(O,H,H)<br />
  93. 93. Table CIP Rules<br /> A table of commonly encountered substituents ranked according to precedence is given on the inside back cover of the text.<br />
  94. 94. Propiedades Físicas de Alquenos<br />
  95. 95. H<br />H<br />C<br />C<br />H<br />H<br />H3C<br />H<br />C<br />C<br />H<br />H<br /> = 0.3 D<br />Dipole moments<br /> What is direction of dipole moment?<br /> Does a methyl group donate electrons to the double bond, or does it withdraw them?<br /> = 0 D<br />
  96. 96.  = 1.4 D<br />H<br />H<br />C<br />C<br />H<br />H<br />Cl<br />H<br />C<br />C<br />H<br />H<br />H3C<br />H<br />C<br />C<br />H<br />H<br /> = 0.3 D<br />Dipole moments<br /> Chlorine is electronegative and attracts electrons.<br /> = 0 D<br />
  97. 97.  = 1.4 D<br />H<br />H<br />C<br />C<br />Cl<br />H<br />H3C<br />H<br />C<br />C<br />Cl<br />H<br />H3C<br />H<br /> = 1.7 D<br />C<br />C<br />H<br />H<br /> = 0.3 D<br />Dipole moments<br /> Dipole moment of 1-chloropropene is equal to the sum of the dipole moments of vinyl chloride and propene.<br />
  98. 98.  = 1.4 D<br />H<br />H<br />C<br />C<br />Cl<br />H<br />H3C<br />H<br />C<br />C<br />Cl<br />H<br />H3C<br />H<br />C<br />C<br />H<br />H<br /> = 0.3 D<br />Dipole moments<br /> Therefore, a methyl group donates electrons to the double bond.<br /> = 1.7 D<br />
  99. 99. R—C+<br />is more stable than<br />H—C+<br />•<br />R—C<br />is more stable than<br />•<br />H—C<br />R—C<br />is more stable than<br />H—C<br />Alkyl groups stabilize sp2 hybridizedcarbon by releasing electrons<br />
  100. 100. Estabilidades Relativas de Alquenos<br />
  101. 101. H<br />R<br />C<br />C<br />H<br />H<br />H<br />R<br />C<br />C<br />C<br />C<br />C<br />C<br />R'<br />H<br />disubstituted<br />Double bonds are classified according tothe number of carbons attached to them.<br />monosubstituted<br />R'<br />H<br />R<br />R<br />R'<br />H<br />H<br />H<br />disubstituted<br />disubstituted<br />
  102. 102. R"<br />R"<br />R<br />R<br />C<br />C<br />C<br />C<br />R'<br />H<br />R'<br />R"'<br />trisubstituted<br />tetrasubstituted<br />Double bonds are classified according tothe number of carbons attached to them.<br />
  103. 103. Substituent Effects on Alkene Stability<br />Electronic<br />disubstituted alkenes are more stable than monosubstituted alkenes<br />Steric<br />trans alkenes are more stable than cis alkenes <br />
  104. 104. Figure Heats of combustion of C4H8isomers.<br />2717 kJ/mol<br />+ 6O2<br />2710 kJ/mol<br />2707 kJ/mol<br />2700 kJ/mol<br />4CO2 + 8H2O<br />
  105. 105. Substituent Effects on Alkene Stability<br />Electronic<br />alkyl groups stabilize double bonds more than H<br />more highly substituted double bonds are morestable than less highly substituted ones.<br />
  106. 106. H3C<br />CH3<br />C<br />C<br />H3C<br />CH3<br />Problem <br />Give the structure or make a molecular model of the most stable C6H12 alkene.<br />
  107. 107. Substituent Effects on Alkene Stability<br />Steric<br />trans alkenes are more stable than cis alkenes<br />cis alkenes are destabilized by van der Waalsstrain <br />
  108. 108. van der Waals straindue to crowding ofcis-methyl groups<br />Figure cis and trans-2-Butene<br />cis-2-butene<br />trans-2-butene<br />
  109. 109. Figure cis and trans-2-Butene<br />van der Waals straindue to crowding ofcis-methyl groups<br />cis-2-butene<br />trans-2-butene<br />
  110. 110. H3C<br />CH3<br />CH3<br />H3C<br />CH3<br />H3C<br />C<br />C<br />C<br />C<br />H<br />H<br />van der Waals Strain<br />Steric effect causes a large difference in stabilitybetween cis and trans-(CH3)3CCH=CHC(CH3)3<br />cis is 44 kJ/mol less stable than trans<br />
  111. 111. Cicloalquenos<br />
  112. 112. Cycloalkenes<br /> Cyclopropene and cyclobutene have angle strain.<br />Larger cycloalkenes, such as cyclopenteneand cyclohexene, can incorporate a double bond into the ring with little or no angle strain. <br />
  113. 113. H<br />H<br />H<br />H<br />Stereoisomeric cycloalkenes<br />cis-cyclooctene and trans-cycloocteneare stereoisomers<br />cis-cyclooctene is 39 kJ/ mol more stablethan trans-cyclooctene<br />cis-Cyclooctene<br />trans-Cyclooctene<br />
  114. 114. H<br />H<br />Stereoisomeric cycloalkenes<br />trans-cyclooctene is smallest trans-cycloalkene that is stable at room temperature<br />cis stereoisomer is more stable than trans through C11 cycloalkenes<br />trans-Cyclooctene<br />
  115. 115. Stereoisomeric cycloalkenes<br />cis and trans-cyclododeceneare approximately equal instability<br />trans-Cyclododecene<br />cis-Cyclododecene<br /> When there are more than 12 carbons in thering, trans-cycloalkenes are more stable than cis.The ring is large enough so the cycloalkene behaves much like a noncyclic one.<br />
  116. 116. Structure and Bonding in Alkynes:sp Hybridization<br />
  117. 117. 120 pm<br />H<br />C<br />C<br />H<br />106 pm<br />106 pm<br />121 pm<br />C<br />CH3<br />C<br />H<br />146 pm<br />106 pm<br />linear geometry for acetylene<br />Structure<br />
  118. 118. C<br />C<br />Cycloalkynes<br />Cyclononyne is the smallest cycloalkyne stable enough to be stored at room temperaturefor a reasonable length of time. <br />Cyclooctyne polymerizeson standing.<br />
  119. 119. Hibridación spy Enlaces en el Acetileno<br />
  120. 120. HC<br />CH<br />Structure of Acetylene<br />C2H2<br />linear<br />bond angles: 180°<br />bond distances: C—H = 106 pm CC = 120 pm<br />
  121. 121. spOrbital Hybridization<br />2p<br />Promote an electron from the 2s to the 2p orbital <br />2s<br />
  122. 122. sp Orbital Hybridization<br />2p<br />2p<br />2s<br />2s<br />
  123. 123. spOrbital Hybridization<br />2p<br />Mix together (hybridize) the 2s orbital and one of the three 2p orbitals<br />2s<br />
  124. 124. sp Orbital Hybridization<br />2p<br />2 p<br />2 sp<br />2 equivalent half-filled sp hybrid orbitals plus 2 p orbitals left unhybridized<br />2s<br />
  125. 125. sp Orbital Hybridization<br />
  126. 126. sp Orbital Hybridization<br /><br />2 p<br /><br />2 sp<br /><br />
  127. 127.  Bonding in Acetylene<br />the unhybridized p orbitals of carbon are involved in separate bonds to the other carbon <br />2 p<br />2 sp<br />
  128. 128.  Bonding in Acetylene<br />
  129. 129.  Bonding in Acetylene<br />
  130. 130.  Bonding in Acetylene<br />
  131. 131. H<br />C<br />C<br />Acidity of Acetyleneand Terminal Alkynes<br />
  132. 132. H2C<br />CH2<br />Acidity of Hydrocarbons<br />In general, hydrocarbons are exceedingly weak acids<br />Compound pKa<br /> HF 3.2<br /> H2O 15.7<br /> NH3 36<br />45<br />CH4 60<br />
  133. 133. HC<br />CH<br />H2C<br />CH2<br />Acetylene<br />Acetylene is a weak acid, but not nearlyas weak as alkanes or alkenes.<br />Compound pKa<br /> HF 3.2<br /> H2O 15.7<br /> NH3 36<br />45<br />CH4 60<br />26<br />
  134. 134. pKa = 60<br />–<br />sp3<br />:<br />C<br />H++<br />H<br />C<br />H<br />sp2<br />:<br />pKa = 45<br />H++<br />C<br />C<br />C<br />C<br />–<br />pKa = 26<br />–<br />sp<br />:<br />H<br />C<br />C<br />C<br />C<br />H++<br />Carbon: Hybridization and Electronegativity<br />Electrons in an orbital with more s character are closer to thenucleus and more strongly held.<br />
  135. 135. NaC<br />CH<br />+<br />+<br />NaOH<br />NaC<br />H2O<br />CH<br />HC<br />CH<br />Sodium Acetylide<br />Objective:<br /> Prepare a solution containing sodium acetylideWill treatment of acetylene with NaOH be effective?<br />
  136. 136. –<br />..<br />..<br />–<br />stronger acidpKa = 15.7<br />weaker acidpKa = 26<br />+<br />CH<br />C<br />:<br />+<br />CH<br />C<br />H<br />:<br />H<br />HO<br />HO<br />..<br />..<br />Sodium Acetylide<br />No. Hydroxide is not a strong enough base to deprotonate acetylene.<br />In acid-base reactions, the equilibrium lies tothe side of the weaker acid.<br />
  137. 137. +<br />+<br />NaNH2<br />NaC<br />NH3<br />CH<br />HC<br />CH<br />–<br />..<br />..<br />–<br />+<br />:<br />:<br />+<br />H2N<br />H<br />H2N<br />CH<br />C<br />CH<br />C<br />H<br />weaker acidpKa = 36<br />stronger acidpKa = 26<br />Sodium Acetylide<br />Solution: Use a stronger base. Sodium amideis a stronger base than sodium hydroxide.<br />Ammonia is a weaker acid than acetylene.The position of equilibrium lies to the right.<br />

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