Introduction to organic chemistry

Introduction to organic chemistry

• 1.
  BY VANA JAGAN MOHANRAO M.S.Pharm, MED.CHEM NIPER-KOLKATA Asst.Professor, MIPER-KURNOOL Email: jaganvana6@gmail.com
• 2.
  Carbon forms ahuge number of compounds. The study of the structures, reactions and properties of these carbon-based compounds is called organic chemistry.  Note: ◦ Carbon monoxide, carbon dioxide, metal carbonates and metal cyanides are not classified as organic compounds. What is Organic Chemistry?
• 3.
  Bonding Nature of Carbon Tetravalent •Carbon forms four bonds. • Due to strong C−C bond, it can bond with itself to form stable straight or branched chains, or ring structures. Strong C−C bonds • C−C bonds are much stronger than bonds between atoms of other elements. Bond Bond energy / kJ mol−1 C−C 350 Si−Si 222 N−N 160 O−O 150 Multiple bonds • Carbon can also form single, double or triple bonds with itself. • Carbon compounds can have varying degree of unsaturation. Why does carbon form so many compounds?
• 4.
  Organic Compounds Aliphatic Alicyclic (closed ring) Open-chain •Straight-chain • Saturated • Unsaturated Aromatic • Branched chain OH O • Contains one or more benzene rings Cl Classification according to Carbon Skeleton
• 5.
  Organic compounds inthe same homologous series: Example: alkene • possess the same general formula CnH2n • differ from the previous member in the series by a −CH2− group CH2=CH2, CH2=CHCH2−H, CH2=CHCH2CH3, CH2=CHCH2CH2CH3 • possess similar chemical properties, due to the presence of same functional group • Alkenes possess a carbon-carbon double bond. • Alkenes undergo electrophilic addition reactions. • show gradual change in physical properties due to increased molecular size and mass, caused by longer carbon chains Etheneb.p. = −102 °C Propeneb.p. = −48 °C 1-Butene b.p. = −6.5 °C 1-Pentene b.p. = 30 °C HOMOLOGOUS SERIES
• 6.
  A functional groupis an atom or a group of atoms that governs the chemical properties of an organic molecule. FUNCTIONAL GROUPS
• 7.
  where R, R1,R2 represent alkyl groups, −CnH2n+1 FUNCTIONAL GROUPS
• 8.
  Class of compoundFunctional group Name of functional group Hydroxy compounds RCH2OH Primary alcohol RR1CHOH Secondary alcohol RR1R2COH Tertiary alcohol C6H5OH Phenol Carbonyl compounds RCHO Aldehyde RR1CO Ketone where R, R1, R2 represent alkyl groups, −CnH2n+1 FUNCTIONAL GROUPS
• 9.
  Class of compoundFunctional group Name of functional group Carboxylic acids RCO2H Carboxylic acid Carboxylic acid derivatives RCOCl Acyl chloride RCO2R1 Ester RCONH2 Amide Amines RNH2 Primary amine RR1NH Secondary amine RR1R2N Tertiary amine Nitriles RC N Nitrile where R, R1, R2 represent alkyl groups, −CnH2n+1 FUNCTIONAL GROUPS
• 10.
   The structuralformulae of organic compounds may be represented using ◦ displayed formulae ◦ condensed structural formulae ◦ skeletal formulae  Note that any structural formula given must give an unambiguous structure. ◦ E.g. 1-propanol ✓CH3CH2CH2OH C3H7OH ✗ Writing Structural Formulae
• 11.
   Displayed Formulae ◦Show both the relative placing of atoms and the number of bonds between them. ◦ All bonds between atoms must be shown. ◦ Exception: The following convention for representing the aromatic ring is preferred: Writing Structural Formulae
• 12.
   Condensed StructuralFormulae ◦ Each carbon atom is written separately. ◦ Following each of these carbon atoms,  the other atoms that are bonded to this carbon atom are written.  Substituent groups that are bonded to this carbon atom are enclosed in brackets. ◦ Similarly, the following convention for representing the aromatic ring is preferred: Writing Structural Formulae
• 13.
   Skeletal Formulae ◦Simplified representation derived from a structural formula by removing hydrogen atoms (and their associated bonds) and carbon atoms from alkyl chains, leaving just the carbon-carbon bonds in the carbon skeleton and the associated functional groups. ◦ The following convention for representing the aromatic ring is preferred: Writing Structural Formulae
• 14.
  Writing Structural Formulae
• 15.
  Writing Structural Formulae
• 16.
   IUPAC Nomenclatureis a system of naming chemical substances developed by the International Union of Pure and Applied Chemistry (IUPAC).  The IUPAC sets global standards for names, symbols, and units used in chemical sciences. IUPAC Nomenclature
• 17.
   The IUPACname for an organic compound consists of the following parts: Root Suffix(es)InfixPrefix(es) No. of carbon atoms in longest continuous carbon chain, i.e. parent chain Nature of parent chain Side chains & functional groups of lower priority 1° suffix Degree of saturation or unsaturation Functional group of highest priority in molecule + 2° suffix IUPAC Nomenclature
• 18.
  root (no. of carbonatoms in parent chain) 1° suffix (degree of saturation) 2° suffix (main functional group, of highest priority) side-chains & functional groups of lower priority, arranged in alphabetical order infix (nature of parent chain) 3-ethyl-4-methylhexane 3-methylcyclopentene 2-hydroxypropanoic acid 3-oxohe x a n al 1 2 3 Locants indicate positions of sustituent groups, bonds etc. in molecule locant locantlocant IUPAC Nomenclature
• 19.
  -3,9-dione root (no. of carbonatoms in parent chain) 1° suffix (degree of saturation) 2° suffix (main functional group, of highest priority) side-chains & functional groups of lower priority, arranged in alphabetical order Locants indicate positions of sustituent groups, bonds etc.in molecule 18-bromo-12-butyl-11-chloro-4,8-diethyl-5-hydroxy-15-methoxytricos-6,13-diene-19-yne tricos 23 carbons IUPAC Nomenclature
• 20.
   Punctuation rules: ◦Di-, tri- etc. are not taken into consideration when arranging side-chains and functional groups alphabetically. ◦ Commas are placed between numbers. ◦ Hyphens are placed between a number and a letter. ◦ All parts are connected either by merging successive names, including commas or hypens to form a one-word name. IUPAC Nomenclature
• 21.
   Functional groupscontrol the chemistry of organic molecules. They contain reactive sites: ◦ Electron deficient sites  E.g. a carbon atom bonded to a more electronegative bromine atom ◦ Electron rich sites  E.g. a π-system in an alkene or a benzene ring ORGANIC REACTIONS
• 23.
  Types of Bond Fission Homolytic •When a covalent bond between two atoms breaks, each atom retains one bonding electron. • Free radicals are formed. • A free radical is an electrically neutral atom or group of atoms that has one unpaired electron. It is unstable and highly reactive. Cl−Cl→Cl + Cl Heterolytic • When a covalent bond between two atoms breaks, one of the atoms retains both the bonding electrons to bear a negative charge. • The other atom bears a positive charge. H−Cl→ H+ + Cl:− ORGANIC REACTIONS
• 24.
  Types of Reagents Nucleophile • Areagent that is attracted to regions of positive charge or electron deficient sites • An electron pair donor • Good bases are generally good nucleophiles Negative ions: H−O:−,N C:− Neutral molecules: H2O:, :NH3 • A reagent that is attracted to regions of negative charge or high electron density • An electron pair acceptor Electrophile 2Positive ions: NO + δ+ end of an induced dipole: Br−Brδ+ δ− δ+ end of a permanent dipole: δ+H−Clδ− ORGANIC REACTIONS
• 25.
   Isomers aremolecules that have the same molecular formula but differentarrangement of atoms in space. ISOMERISM Structural isomerism • Same molecular formula • Different structural formulae Stereoisomerism • Same molecular formula • Same structural formula • Different spatial arrangement of atoms in 3D space Chain isomerism Functional isomerism Positional isomerism Cis-trans isomerism Optical isomerism ISOMERISM
• 26.
   Chain Isomerism ◦Arises due to the different arrangement of carbon atoms in a carbon chain. ◦ E.g. isomers of hexane, C6H14 STRUCTURAL ISOMERISM
• 27.
   Positional Isomerism ◦Arises due to the different positions assumed by a functional group on a carbon chain or ring. OH OH pentan-1-ol pentan-2-ol O H pentan-3-ol CH3 Cl CH3 CH3 2-chloromethylbenzene Cl 3-chloromethylbenzene Cl 4-chloromethylbenzene STRUCTURAL ISOMERISM
• 28.
  STRUCTURAL ISOMERISM
• 29.
   Cis-trans (a.k.a.geometric) isomerism [Use of E-Z nomenclature is not required.] ◦ Criteria:  Restricted rotation about a double bond, e.g. carbon- carbon double bond, or  Restricted rotation due to a rigid ring structure  Two different substituent groups attached to each atom in a double bond, e.g. to each carbon atom in a carbon-carbon double bond STREOISOMERISM
• 30.
  Examples of cis-transisomers arising from: Restricted rotation about a double bond STREOISOMERISM
• 31.
  Examples of cis-transisomers arising from: Rigid ring structure STREOISOMERISM
• 32.
   Optical isomerism ◦Criteria:  A chiral carbon, i.e. an asymmetrical carbon atom with four different substituent groups  No plane of symmetry ◦ Optical isomers exist as a pair of non– superimposable mirror images of each other. ◦ Optical isomers are also known as enantiomers. STREOISOMERISM
• 33.
   Enantiomers ◦ Identicalchemical properties and physical properties ◦ Rotate plane of polarised light in opposite directions STREOISOMERISM
• 34.
   Racemic mixture ◦Equal amounts of both enantiomers. ◦ Optically inactive, as there is no net rotation of plane- polarised light. Although both enantiomers rotate plane- polarised light in opposite directions, the rotations cancel out.
• 35.
   Drawing opticalisomers ◦ Optical isomers must be drawn as three- dimensional structures according to the convention used in the example below: STREOISOMERISM