214 ALKYNES 9.17Three isomers have unbranched carbon chains: CH2CH2CH2CH2C≡CHCH3CH2CH2C≡CCH3CH2CHC≡CCH2CH3 1-Hexyne 2-Hexyne Next consider all the alkynes with a single methyl branch CH3CHCH2C≡CHCH3CH2CHC≡ CH CH3CHO≡CCH2 H3 4-Methyl-l-pentyne 3-Methyl-l-pentyne 4-Methyl-2-pentyne One isomer has two methyl branches. None is possible with an ethyl branch CH2CC≡CH 3.3-Dimethyl-1-butyne 9. 18(a) CH CH, CHaCECH is 1-pentyne (b) CH CH,CECCH, is 2-pentyne (c) CH_ C=CCHCHCH3 is 4, 5-dimethyl-2-hexyne H3C CH (d) H, CH,CH, CECH is 5-cyclopropyl-l-pentyne CECCHos is cyclotridecyne (e) (f) CHCH, CH,CH, CHCH,CH, CH,CH, CH3 is 4-butyl-2-nonyne (Parent chain must contain the triple bond. H3 (g) CH CC=CCCH3 is 2, 2,5,5-tetramethyl-3-hexyne CH3 CH 9. 19 (a) 1-Octyne is HCECCH, CH,CH,CH, CH, CH (b) 2-Octyne is CH C=CCH,CH,CH,CH,CH (c) 3-Octyne is CH CH,C=CCH, CH, CH, CH3 (d) 4-Octyne is CH_CH,CH,C=CCH, CH,CH3 (e) 2, 5-Dimethyl-3-hexyne is CH CHCECCHCH () 4-Ethyl-1-hexyne is CH3 CH2CHCH,CECH CHCH Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
9.17 Three isomers have unbranched carbon chains: Next consider all the alkynes with a single methyl branch: One isomer has two methyl branches. None is possible with an ethyl branch. 9.18 (a) (b) (c) (d) (e) ( f ) (g) 9.19 (a) (b) (c) (d) (e) ( f ) 4-Ethyl-1-hexyne is CH3CH2CHCH2C CH2CH3 CH 2,5-Dimethyl-3-hexyne is CH3CHC CH3 CCHCH3 CH3 4-Octyne is CH3CH2CH2C CCH2CH2CH3 3-Octyne is CH3CH2C CCH2CH2CH2CH3 2-Octyne is CH3C CCH2CH2CH2CH2CH3 1-Octyne is HC CCH2CH2CH2CH2CH2CH3 CH3CC CH3 CH3 CCCH3 is 2,2,5,5-tetramethyl-3-hexyne CH3 CH3 1 2 46 3 5 CH3CH2CH2CH2CHCH2CH2CH2CH2CH3 is 4-butyl-2-nonyne C CCH3 45 6 7 8 9 3 21 (Parent chain must contain the triple bond.) CCH2 2 3 CH2C 13 1 is cyclotridecyne CH2CH2CH2C CH is 5-cyclopropyl-1-pentyne 543 2 1 CH3C H3C CCHCHCH3 is 4,5-dimethyl-2-hexyne CH3 1 2 3 4 5 6 CH3CH2C CCH3 is 2-pentyne 5 4 3 21 CH3CH2CH2C CH is 1-pentyne 543 2 1 CH3CC CH3 CH3 CH 3,3-Dimethyl-1-butyne CH3CHC CH3 CCH3 4-Methyl-2-pentyne CH3CH2CHC CH3 CH 3-Methyl-1-pentyne CH3CHCH2C CH3 CH 4-Methyl-1-pentyne CH3CH2CH2CH2C CH CH3CH2CH2C CCH3 CH3CH2C CCH2CH3 1-Hexyne 2-Hexyne 3-Hexyne 214 ALKYNES Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
215 (8) Ethynylcyclohexane is C≡CH CH3 (h) 3-Ethyl-3-methyl-l-pentyne is CH,CH,CC=CH CHCH 9.20 Ethynylcyclohexane has the molecular formula C&Hi. All the other compounds are CHi 9.21 Only alkynes with the carbon skeletons shown can give 3-ethy lhexane on catalytic hydrogenation 9.22 The carbon skeleton of the unknown acetylenic amino acid must be the same as that of homoleucine The structure of homoleucine is such that there is only one possible location for a carbon-carbon triple bond in an acetylenic precursor. HC≡ CCHCH,CHCO CH CHCHCHCHCO CHNI ChInO Homoleucine 9.23 (a) CH, CH-CH_CH2 CH- CHCI2 2.. NW, CH3 CH,CH_CHIC=CH hexyne 1. NaNH. NH CH CH, CH,CH, CH=CH2 CH CH, CHCH, CHCH, Br CH2CH2CH2CHC≡CH 2-Dibromohexane l-Hexyne HC≡CH HC≡ C Na* CH,CH2 CH- CH,Br CH2CH2CH2CHC≡CH (d) CH_CH__,CH,I DMSO CH3 CH,CH,CH,CHECH I-lodohexane -Hexene 1-Hexene is then converted to l-hexyne as in part(b). 9. 24 (a) Working backward from the final product, it can be seen that preparation of 1-butyne will allow the desired carbon skeleton to be constructed CHaCH,=CCH,CH3 prepared from CH,CH,CEC: BrCH,CH3 3-Hexyne Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
(g) (h) 9.20 Ethynylcyclohexane has the molecular formula C8H12. All the other compounds are C8H14. 9.21 Only alkynes with the carbon skeletons shown can give 3-ethylhexane on catalytic hydrogenation. 9.22 The carbon skeleton of the unknown acetylenic amino acid must be the same as that of homoleucine. The structure of homoleucine is such that there is only one possible location for a carbon–carbon triple bond in an acetylenic precursor. 9.23 (a) (b) (c) (d) 1-Hexene is then converted to 1-hexyne as in part (b). 9.24 (a) Working backward from the final product, it can be seen that preparation of 1-butyne will allow the desired carbon skeleton to be constructed. CH3CH2C CCH2CH3 3-Hexyne CH2CH2C C prepared from BrCH2CH3 CH3CH2CH2CH2CH CH2 1-Hexene CH3CH2CH2CH2CH2CH2I 1-Iodohexane KOC(CH3)3 DMSO HC CH Acetylene CH3CH2CH2CH2C CH 1-Hexyne CNa HC NaNH2 NH3 CH3CH2CH2CH2Br 1-Hexene 1,2-Dibromohexane CH3CH2CH2CH2CH CH2 CH3CH2CH2CH2C CH 1-Hexyne Br2 CCl4 1. NaNH2, NH3 2. H2O CH3CH2CH2CH2CHCH2Br Br 1. NaNH2, NH3 2. H2O CH3CH2CH2CH2CH2CHCl2 1,1-Dichlorohexane CH3CH2CH2CH2C CH 1-Hexyne HC CCHCH2CHCO CH3 NH3 O CH3CH2CHCH2CHCO CH3 NH3 O H2 Pt C7H11NO2 Homoleucine H2 Pt or or 3-Ethyl-1-hexyne 4-Ethyl-1-hexyne 4-Ethyl-2-hexyne 3-Ethylhexane 3-Ethyl-3-methyl-1-pentyne is CH3CH2CC CH2CH3 CH3 CH Ethynylcyclohexane is CH C ALKYNES 215 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website