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Page 1 ? Preparation of Alkanes : (1) From unsaturated hydrocarbons : (2) Wurtz reaction R–X + 2Na + X–R R–R + 2 NaX (3) Decarboxylation : [Sodium salt of carboxylic acid + NaOH + CaO ? Alkane [n c = 1 less] Page 2 ? Preparation of Alkanes : (1) From unsaturated hydrocarbons : (2) Wurtz reaction R–X + 2Na + X–R R–R + 2 NaX (3) Decarboxylation : [Sodium salt of carboxylic acid + NaOH + CaO ? Alkane [n c = 1 less] (4) Kolbe’s Electrolysis : Current Potassiumsalt of carboxylicacid(aq) Higher alkane ?? ????? ?? ?? ? Chemical Properties of Alkanes : (1) Halogenation : One (H) atom is replaced by halogen at a time. CH 4 (g) + Cl 2 (g) CH 3 Cl + CH 2 Cl 2 + CHCl 3 + CCl 4 (2) Aromatization : n-Hexane ? Preparation of alkenes : (1) From alkynes [Alkyne + H 2 — ? Alkene] (2) From alkyl halide by (dehydrohalognation) Page 3 ? Preparation of Alkanes : (1) From unsaturated hydrocarbons : (2) Wurtz reaction R–X + 2Na + X–R R–R + 2 NaX (3) Decarboxylation : [Sodium salt of carboxylic acid + NaOH + CaO ? Alkane [n c = 1 less] (4) Kolbe’s Electrolysis : Current Potassiumsalt of carboxylicacid(aq) Higher alkane ?? ????? ?? ?? ? Chemical Properties of Alkanes : (1) Halogenation : One (H) atom is replaced by halogen at a time. CH 4 (g) + Cl 2 (g) CH 3 Cl + CH 2 Cl 2 + CHCl 3 + CCl 4 (2) Aromatization : n-Hexane ? Preparation of alkenes : (1) From alkynes [Alkyne + H 2 — ? Alkene] (2) From alkyl halide by (dehydrohalognation) Carbon attached with halogen is a-carbons Carbon attached with a-carbons is ß-carbons Halogen is removed and ‘H’-atom is removed from ß-carbon to form (C = C) double bond. (3) By dehydration of alcohols (Loss of water molecule) Carbon attached to alcohoic group is a-carbon. Carbon attached to a-carbon is ß-carbon. (4) From vicinal dihalides [Compounds in which halogen atom are attached with adjacent carbons] ? Chemical Properties of Alkenes : (1) Addition of Halogens : (2) Addition of H—X : (A) Markownikov’s rule (M.R.) : During electrophillic addition of hydrogen halide, the electron deficient electrophile (E + ) always attack Page 4 ? Preparation of Alkanes : (1) From unsaturated hydrocarbons : (2) Wurtz reaction R–X + 2Na + X–R R–R + 2 NaX (3) Decarboxylation : [Sodium salt of carboxylic acid + NaOH + CaO ? Alkane [n c = 1 less] (4) Kolbe’s Electrolysis : Current Potassiumsalt of carboxylicacid(aq) Higher alkane ?? ????? ?? ?? ? Chemical Properties of Alkanes : (1) Halogenation : One (H) atom is replaced by halogen at a time. CH 4 (g) + Cl 2 (g) CH 3 Cl + CH 2 Cl 2 + CHCl 3 + CCl 4 (2) Aromatization : n-Hexane ? Preparation of alkenes : (1) From alkynes [Alkyne + H 2 — ? Alkene] (2) From alkyl halide by (dehydrohalognation) Carbon attached with halogen is a-carbons Carbon attached with a-carbons is ß-carbons Halogen is removed and ‘H’-atom is removed from ß-carbon to form (C = C) double bond. (3) By dehydration of alcohols (Loss of water molecule) Carbon attached to alcohoic group is a-carbon. Carbon attached to a-carbon is ß-carbon. (4) From vicinal dihalides [Compounds in which halogen atom are attached with adjacent carbons] ? Chemical Properties of Alkenes : (1) Addition of Halogens : (2) Addition of H—X : (A) Markownikov’s rule (M.R.) : During electrophillic addition of hydrogen halide, the electron deficient electrophile (E + ) always attack on that doubly/triply bounded carbon atom. which already has greater number of hydrogen atoms. (B) Peroxide/Kharasch effect (Anti M.Rule) : This effect takes place in presence of organic peroxides when the hydrogen free radical attacks on that doubly bonded carbon which has lesser number of hydrogen atoms. (3) Ozonolysis In this reaction all those carbons which form double bonds get finally converted into carbonyl carbons. If alkenes are symmetrical then both carbonyl compounds are same. If more than two double bonds are present then we get atleast one compound which has two carbonyl groups at the end. Such bifunctional compounds are formed from that part of alkene which is in between the double bonds. For cyclic alkenes : Page 5 ? Preparation of Alkanes : (1) From unsaturated hydrocarbons : (2) Wurtz reaction R–X + 2Na + X–R R–R + 2 NaX (3) Decarboxylation : [Sodium salt of carboxylic acid + NaOH + CaO ? Alkane [n c = 1 less] (4) Kolbe’s Electrolysis : Current Potassiumsalt of carboxylicacid(aq) Higher alkane ?? ????? ?? ?? ? Chemical Properties of Alkanes : (1) Halogenation : One (H) atom is replaced by halogen at a time. CH 4 (g) + Cl 2 (g) CH 3 Cl + CH 2 Cl 2 + CHCl 3 + CCl 4 (2) Aromatization : n-Hexane ? Preparation of alkenes : (1) From alkynes [Alkyne + H 2 — ? Alkene] (2) From alkyl halide by (dehydrohalognation) Carbon attached with halogen is a-carbons Carbon attached with a-carbons is ß-carbons Halogen is removed and ‘H’-atom is removed from ß-carbon to form (C = C) double bond. (3) By dehydration of alcohols (Loss of water molecule) Carbon attached to alcohoic group is a-carbon. Carbon attached to a-carbon is ß-carbon. (4) From vicinal dihalides [Compounds in which halogen atom are attached with adjacent carbons] ? Chemical Properties of Alkenes : (1) Addition of Halogens : (2) Addition of H—X : (A) Markownikov’s rule (M.R.) : During electrophillic addition of hydrogen halide, the electron deficient electrophile (E + ) always attack on that doubly/triply bounded carbon atom. which already has greater number of hydrogen atoms. (B) Peroxide/Kharasch effect (Anti M.Rule) : This effect takes place in presence of organic peroxides when the hydrogen free radical attacks on that doubly bonded carbon which has lesser number of hydrogen atoms. (3) Ozonolysis In this reaction all those carbons which form double bonds get finally converted into carbonyl carbons. If alkenes are symmetrical then both carbonyl compounds are same. If more than two double bonds are present then we get atleast one compound which has two carbonyl groups at the end. Such bifunctional compounds are formed from that part of alkene which is in between the double bonds. For cyclic alkenes : (D) With potassium paramagnate : (i) Cold dilute alkaline KMnO 4 = Bayer’s reagent. [ ] 4 Alkene+colddil.KMnO Diol ? Bayer’s test for the presence of (C = C) bond Compound + cold dil. alk. KMnO 4 —? Purple colour decolourised ? Compound is alkene. (ii) Hot KMnO 4 + Hot KMnO 4 + Alkynes ? Preparation : (1) CaC 2 + 2H 2 O —? Ca(OH) 2 + HC = CH Calcium carbide Acetylene (2) From vicinal dihalides ? Chemical properties : (1) Hydration [Addition of water] — —Read More
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