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Organic Chemistry
 

Organic Chemistry

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    Organic Chemistry Organic Chemistry Presentation Transcript

    • HydrocarbonsThose compounds which contain only carbonand hydrogen.There are two types of hydrocarbons:1- saturated hydrocarbons: in which allcarbon bonds are sigma (σ)bonds,include alkanes and cycloalkanes.
    • 2- unsaturated hydrocarbons: which contain sigmaas well as pi-bonds, include alkenes (paraffin) andAlkynes (acetylenes).
    • Nomenclature of organic :compoundsThe IUPAC rules for alkanes3. The general name for acyclic saturated hydrocarbon is Alkanes. The – ane ending is used for all saturated hydrocarbons
    • 2: alkanes without branches arenamed according to the number ofcarbon atoms.
    • CH4 MethaneCH3CH3 EthaneCH3CH2CH3 PropaneCH3(CH2)2CH3 n- butaneCH3(CH2)3CH3 n- pentaneCH3(CH2)4CH3 n- hexaneCH3(CH2)5CH3 n- heptaneCH3(CH2)6CH3 n- octaneCH3(CH2)7CH3 n- None
    • 3: for alkanes with branchedchains, the root nameIs that of the longest continuouschain of carbon atoms, forexample CH3CH CHCH2CH3 CH3CH3
    • The longest continuous chain(colored C’s) has five carbonatoms .the compound is thereforenamed as substituted pentane.
    • 4: Groups attached to themain chain are calledsubstituents. Saturatedsubstituens that containonly carbon and hydrogencalled alkyl groups
    • Alkyl groups- CH3 Methyl- CH2CH3 Ethyl- CH2CH2CH3 n-Propyl CH3CHCH3 isopropyl
    • Other substituent• -OH • Hydroxy• -NO2 • Nitro• -OCH3 • Methoxy• -CN • Cyano• -Cl • Chloro• -Br • Bromo• -F • Flouro• -I • Iodo• -NH2 • Amino
    • In the example, each branch has onlyone carbon. derived from thehydrocarbon methane by removingone of the hydrogens, it is called themethyl group.CH3- or Me-
    • 5: groups are located by a name andnumber.The main chain is numbered in such a waythat the first substituent receive the lowestpossible number.` 1 2 3 4 5 CH3 CH CH CH2 CH3 CH3 CH3
    • When two identical groups areattach to the main chain, prefixessuch as di, tri, and tetra- are used.The previous compound is correctlynamed as 2,3 - dimethylpentane
    • 6: Punctuation is important inwriting IUPAC names .Thenames are written as one word.Numbers are separated fromeach other by commas andfrom letters by hyphens.
    • If two or more different types ofsubstituents are present, they arelisted alphabetically, except thatprefixes such as di- and tri- are notcounted for alphabetizing.
    • Examples:Give the IUPAC name for the followingcompounds.A: CH3 CH CH2 CH3 CH3 CH3B: CH3 CH2 CH CH3 C: CH3– C-CH3 NO2 CH3
    • D) CH3C(CH3)3 E) BrCH2CH2CHCl2
    • CycloalkanesCarbocyclic hydrocarbons that arenamed by placing the prefix cyclo-before the alkane name correspondingto the number of carbon atoms in thering.
    • Cyclopropane cyclobutane cyclopentaneCyclohexane cyclooctane
    • When the ring carry alkyl or halogen substituents, they are named in the usual way. CH3 CH3 CH3 CH3 CH3Methylcyclopropane 1,1-dimethylcyclopentane 1,2-dimethylcyclopentane
    • Alkenesare hydrocarbons that contain onedouble bond, When the molecule containtwo double bonds it is often called a diene
    • CH2=CH2 Ethene (ethylene)CH2=CH-CH3 PropeneCH2=CH-CH2-CH3 Butene-1CH3-CH=CH-CH3 Butene-2
    • CH3 CH3cyclopentene 1-methylcyclopentene 3-methylcyclohexene
    • Preparation of alkenesThe most used methods forpreparations of alkenes andalkynes are based onelimination reactions elimination C C C C Y Z alkene
    • 1- dehydrogenation This reaction includes removal of hydrogen from saturated hydrocarbons in presence of a catalyst and at high temperature e.gH3C Cr2O 3/Al 2O 3 H3C CH3 + CH3 H2C + H2 CH3
    • dehalogenation-2The reaction includes removal ofhalogen of 1,2- dihalogenderivatives of alkanes by meansof Zn dust and methanol H3C CHBr Zn CH3OH CH3-CH=CH2 + ZnBr2BrH2C
    • 3- Dehydration: Dehydration of secondary and tertiaryalcohol using dilute sulphuric acid CH3CH2CHOHCH3 CH3CH=CHCH3 + H2O
    • 4- DehydrohalogenationBy the action of ethanolic potassiumhydroxide on alkyl halides, eg propene frompropyl bromide KOHCH3CHBrCH3 CH2=CHCH3 KOHCH3CH2CHBrCH3 CH3CH=CHCH3
    • Chemical properties of alkenesOwing to the presence of the double bondthe alkenes undergo addition reactions C=C + E – Nu C+ CE CNu CE
    • 1-HydrogenationAlkenes are hydrogenated underpressure of hydrogen at the presenceof a catalyst catalystCH2 = CH2 + H2 CH3 - CH3
    • 2- HydrationAlkenes are catalytically hydratedin dilute acid solution givingalcohols H+CH3CH =CH2 + H2O CH3CHOHCH3
    • 3- HalogenationChlorine and bromine are readily addeto the double bond in the darkCH2 = CH2 + Br2 CH2Br – CH2Br
    • alkynes NomenclaturesAlkynesName Formula Structural FormulaEthyne C2 H 2 CH ≡ CH(Acetylene)Propyne C3 H 4 CH≡ C-CH31-Butyne C4 H 6 CH≡ C-CH2-CH32-Butyne C4 H 6 CH3-C≡ C-CH3
    • General methods for preparation of alkynes1- By the action of potassium hydroxideon gem or Vicinal dihalidethe reaction proceeds in two steps ethanolBrCH2CH2Br + KOH CH2=CHBr ethanolCH2= CHBr + KOH CH≡CH+2KBr+H2O Acetylene
    • 2- DehalogenationBy the action of zinc dust and heat ontetrahalogeno alkanesCH3CBr2-CHBr2 + 2 Zn Heat -2ZnBr2 CH3 – C≡ CH
    • Chemical properties of alkynes :Undergo the same reaction as alkenes butusing two moles of the reagent1- CH3C = CH 2H2/Pd CH3CH2CH3Propyne n- propane 2Cl22- CH = CH + Cl2CH-CHCl2 2HBr3- CH3C = CH CH3CBr2CH3
    • Aromatic hydrocarbonsAromatic are cyclic, they are unsaturated,usually have three conjugated double bonds foreach ring of carbon atoms , not all aromatic arehydrocarbon e.g pyridine N Pyridine
    • BenzeneBenzene is the an example for aromatichydrocarbons.Benzene has six pi electrons two from eachof the double bonds benzene
    • Fused ring systemThose are aromatic similar to benzene with morethan one benzene ring e.g naphthalein andanthracene anthracene naphthalene
    • Substituted benzeneThe benzene ring minus one hydrogen (C6H5-)is named as phenyl group. In general groupderived from aromatic compounds by removingOne hydrogen from carbon called aryl group.When one hydrogen replaced by other group iscalled monosubstituted
    • O OH O H Cl CH3chlorobenzene benzoic acid toluene benzaldehyde O NH2 NH2 OCH3 benzamide aniline anisole
    • Cl CH3 Cl CH31,2-dichlorobenzene o-xylene O OH OH 2-hydroxyben zoic acid
    • Reactions of Benzene•Benzene is always stable because of its delocalized (π) bonds.•Benzene is therefore chemically less reactivethan unsaturated aliphatic hydrocarbons.
    • (1) Halogenation: Br F e B r2 Br2 + HBr+
    • (2) Nitration: NO 2 H 2S O 4+ HNO3 + H2 O
    • (3) Sulphonation: SO3H+ H 2S O + H2O 4 Benzene sulphonic acid
    • (4) Alkylation: CH3+ CH3Cl + HCl