Dolbier HW Solutions 216

Dolbier HW Solutions 216 - 210 ALKYNES 9.3 The bonds become...

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210 ALKYNES 9.3 The bonds become shorter and stronger in the series as the electronegativity increases. NH 3 H 2 OH F Electronegativity: N (3.0) O (3.5) F (4.0) Bond distance (pm): N @ H (101) O @ H (95) F @ H (92) Bond dissociation energy (kJ/mol): N @ H (435) O @ H (497) F @ H (568) Bond dissociation energy (kcal/mol): N @ H (104) O @ H (119) F @ H (136) 9.4 ( b ) A proton is transferred from acetylene to ethyl anion. The position of equilibrium lies to the right. Ethyl anion is a very powerful base and depro- tonates acetylene quantitatively. ( c ) Amide ion is not a strong enough base to remove a proton from ethylene. The equilibrium lies to the left. ( d ) Alcohols are stronger acids than ammonia; the position of equilibrium lies to the right. 9.5 ( b ) The desired alkyne has a methyl group and a butyl group attached to a @ C > C @ unit. Two alkylations of acetylene are therefore required: one with a methyl halide, the other with a butyl halide. It does not matter whether the methyl group or the butyl group is introduced f rst; the order of steps shown in this synthetic scheme may be inverted. ( c ) An ethyl group and a propyl group need to be introduced as substituents on a
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