Octynes 3- octyne

C24K is a moderately active catalyst for hydrogenation of alkenes. It is a very efficient catalyst for isomerization of cw-stilbene to trcnj-stilbene. It is also effective for isomerization of alkynes 2-octyne-> 1-octyne (86% yield). An allene is a probable intermediate 2-decyne -> 1-decyne (207o) and 1,2-decadiene (9%,). Potassium alone also effects these isomerizations, but only at higher temperatures. Benzene is slowly converted into biphenyl when in contact with C24K in refluxing cyclohexane. This reaction has also been reported for CgK in DMF at 20 (61%, yield).=... 

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. 

---