Octynes

J-unsaturated ester is formed from a terminal alkyne by the reaction of alkyl formate and oxalate. The linear a, /J-unsaturated ester 5 is obtained from the terminal alkyne using dppb as a ligand by the reaction of alkyl formate under CO pressure. On the other hand, a branehed ester, t-butyl atropate (6), is obtained exclusively by the carbonylation of phenylacetylene in t-BuOH even by using dppb[10]. Reaction of alkynes and oxalate under CO pressure also gives linear a, /J-unsaturated esters 7 and dialkynes. The use of dppb is essen-tial[l 1]. Carbonylation of 1-octyne in the presence of oxalic acid or formic acid using PhiP-dppb (2 I) and Pd on carbon affords the branched q, /J-unsatu-rated acid 8 as the main product. Formic acid is regarded as a source of H and OH in the carboxylic acids[l2]. 

Octyne is prepared as described in Problem 9 9 and converted to 4 octanone by hydration with H2O H2SO4 and HgS04... 

Property Dimethyl-hexyned Dimethyl-octyn Tetramethyl-decynedi ... 

Dtisopropyl ketone 2,4-Diniethyl-3-pentanone 1.32 C7H14O 1-Octyne 55 QHk... 

C8H14 1-OCTYNE 79.739 5.0705E-01 4.5503E-05 235.39 372 C9H10 ALPHA-METHYL- 111.072 3.1472E-01 3.7121 E-05 208.53... 

Reaction of 4-octyne with trifiuoroacetic acid in CH2CI2 containing 0.1-1.0A/Br leads mainly to Z-4-bromo-4-octene by an anti addition. The presence of Br greatly accelerates the reaction as compared to reaction with trifiuoroacetic acid alone, indicating the involvement of the Br in the rate-determining step. ... 

Octyne and 2-octyne also give >95% anti addition vinder these conditions. The reactions are formulated as concerted Ad S processes. 

Display 1-octyne as a ball-and-spoke model. Examine the individual vibrations (> 1400 cm only), and classify the bands in the experimental infrared spectrum as due to specific motions, e.g., CH, CC and C=C stretching, and HCH and CCC bending motions. 

---