![Formation of alkanes
HC ≡ CH + H2 → [CH2 = CH2] → CH3-CH3
Acetylen heated with hydrogen gase in
presence of catalyst Renay Ni, ethane is
formed. Hydrogenation further carried
give alkane.](https://image.slidesharecdn.com/hjwuc7djtjkovmoiegxa-signature-899ce1189b4e53b138b4fd78f98ec9f38bed324a22c74ca5f1541ee863d546a6-poli-171223164112/85/Alkyne-34-320.jpg)
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Alkyne
The document discusses the electronic structure, nomenclature, uses, methods of preparation, and reactions of ethyne (acetylene). It notes that a triple bond is stronger than a double bond which is stronger than a single bond. Acetylene is used in welding, lighting, and fruit ripening. It can be prepared from calcium carbide, vicinal/geminal dihalides, or tetrahalides. Reactions include hydrogenation to form alkanes and ozonolysis. Polymerization can form benzene from multiple acetylene molecules.
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Alkyne
- 9. Electronic structure ofethyne • M.F • Sigma and pi bond • Triple bond > double bond > single bond. • 823 Kj mol > 681 KJ mol > 348 KJ mol. • 120 pm > 133 pm > 154pm • Bond enthalpy (Bond energy) and bond length. • But based on priority prefer first = bond.
- 12. Nomenclature of alkyne •Common name- acetylene • IUPAC name- alk – alk • If 2 triple bond- diyne and 3 triple bond- triyne. • Double bond and triple bond both first prefer double bond and triple bond. eg. But-1en-3-yne.
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- 21. Uses of acetylene •Use as oxyacetylene flame which used as welding of metal.
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- 24. Manufacture of wastronand wastrosol • Poison gas. • Manufacture of acetaldehyde, acetic acid, oxalic.
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- 26. Method of preparationof alkyne • From CaC2 • From vicinal dihalide and Geminal dihalide • From tetrahalide
- 27. From calcium carbide •Industrial method. • Impurities of phosphine(PH3) and hydrogen sulphide(H2S) are remove by passing acetylene through CuSO4 solution. HO-H + C = C + H-OH → +Ca(OH)2 Ca
- 28. From vicinal andGeminal dihalide • By dehydrohalogenation.
- 29. From vicinal andGeminal dihalide • From vicinal dihalide:- Ethylene dibromide + KOH to give vinyl bromide further react with NaNH2(Sodamide) to give ethylene. • From Geminal dihalide:- 1,1 dibromoethane + alc KOH to give vinyl bromide further react with NaNH2 to give ethylene.
- 30. From vicinal andGeminal dihalide • Weak base give poor yield. • Strong base give strong yield.eg. NaNH2. • 1,2-Dibromo ethane + 2NaNH2 to give ethylene + 2NaBr + 2NH3. • 1,1-Dibromo ethane + 2NaNH2 to give same.
- 31. From tetrahalide • Dehalogenation. •Ethylene tetrabromide(1,1,2,2- tetrabromoethane) + 2Zn in presence of alcohol to give ethyne + 2ZnBr2.
- 32. Physical properties ofalkynes • C2-C3 – gas • C4-C8- liquid • C9- more- solid • Odour- except C2 all odourless. • High B.P & M.P & mass & polar. • Insoluble in water but soluble in solvent.
- 33. Reaction of acetylene •Formation of alkanes (Hydrogenation) • Ozonolysis • Formation of benzene
- 34. Formation of alkanes HC≡ CH + H2 → [CH2 = CH2] → CH3-CH3 Acetylen heated with hydrogen gase in presence of catalyst Renay Ni, ethane is formed. Hydrogenation further carried give alkane.
- 35. polymerisation • Formatin ofbenzen 3CH ≡ CH → benzene.