Basic Principles Of Organic Chemistry PDF

1 Basic Principle of Organic CHEMISTRY Lec (3)  Alkenes They are hydrocarbons containing double bond. they have the general formula (CnH2n) Nomenclature IUPAC system 1- Chose the longest carbon chain containing the double...

1 Basic Principle of Organic CHEMISTRY Lec (3)  Alkenes They are hydrocarbons containing double bond. they have the general formula (CnH2n) Nomenclature IUPAC system 1- Chose the longest carbon chain containing the double bond and number the chain to give the d.b the lowest number. 2- The name will be as in the following: 3- If the d.b repeated many times, we denote the number by adding Di, Tri, Tetra…..etc Examples  Common system - Only for unbranched chain with d.b at C1. Examples Nomenclature of Cycloalkene  Geometrical isomerism - The difference between the compound resulted due to arrangement around double bond. Examples - In presence of four different groups around the double bond, the groups will be ranked according to atomic weight priority. - If one of the double bonded C. atom attached to two similar atoms or groups, there will be no geometrical isomerism. as 1-Butene, isobutene 1-Butene Iso-butene Preparation of alkenes (By elimination reaction) 1- Dehydrohalogenation of alkyl halides  Saytzef rule In elemination reaction the H. atom taken from the carbon containing the less number of H. atoms. 2- Dehydration of alcohols Mechanism Mechanism 3- Dehalogenation of vicinal dihalides 4- Kolb electrolysis 5- Reduction of alkynes 12 Reactions of alkenes 1- Addition reactions i- Addition of hydrogen ii- Addition of halogen Mechanism of halogen addition iii- Addition of hydrogen halide For symmetrical alkenes For unsymmetrical alkenes Markovnikov’s rule In addition reactions, the H.atom will be added on the hydrogen rich C. atom. Mechanism Anti-Markovnikov’s addition Mechanism iv- Addition of H2SO4 The addition follows Markovnikov’s rule. We can consider it addition of HOH catalyzed by H2SO4. v- Halohydrine addition Addition of halogen in presence of HOH. - For unsymmetrical alkenes, the halogen will bond to the hydrogen rich C. atom. vi- Dimerization Mechanism - The H. atom removed according to Saytzef rule. vii- Polymerization 2- Oxidation reactions a) Oxidation without cleavage of double bond i- Hydroxylation (Glycol formation) Using cold aq. KMnO4 or OsO4. Mechanism ii- Addition of oxygen Using O2/Ag2O or Ph-CO3H as an oxidizing agents. b) Oxidation with cleavage of double bond i- Using alkaline KMnO4 ii- Ozonolysis Mechanism 3- Substitution reactions Mechanism  Alkynes (CnH2n-2) Nomenclature IUPAC system 1- Chose the longest carbon chain containing the triple bond and number the chain to give the d.b the lowest number. 2- The name will be as in the following: Examples Common system - All alkynes are derived from acetylene: Preparation of alkynes 1- Dehydrohalogenation of dihalides 2- From acetylene - In this method we raise the carbon chain of terminal alkynes. 3- From calcium carbide 4- Kolb electrolysis Reactions of alkynes i- Addition of halogen ii- Addition of H2  iii- Addition of hydrogen halide - The reaction takes place in two step according to Markovnikov’s rule iv- Addition of HCN v- Addition of H2O - Double bond C.atom containing –OH group is unstable (Enol form) converted into its stable (Keto form) - Addition of water to any other alkyne than acetylene will give a ketone  vi- Reaction as acids - The terminal hydrogen of the terminal alkynes usually acts as acidic hydrogen. - Non-terminal alkynes doesn’t give this reaction. vii- Ozonolysis viii- Oxidation - Double bond could be oxidized faster than triple bond. ix- Polymerization a- Formation of benzene b- Linear polymerization