Alkyne Reactions

Exam 4 material

H₂ and Pt/Ni/Pd

forms alkane

H₂ and Lindlar’s catalyst

forms cis alkene

Na(s) and NH₃(l)

forms trans alkene

mechanism involves radicals and electron repulsion creates trans alkene

1 eq of HX

adds 1 X to more substituted end of alkyne to create an alkene

excess HX

adds 2 X’s to more substituted end of alkyne to create an alkane

HgSO₄ and H₂SO₄

forms ketone from an enol intermediate

tautomerization of enol makes ketone

9-BBN and H₂O_2, NaOH

forms aldehyde from an enol intermediate

anti-markonikov product

tautomerization of enol makes aldehyde

X₂ and CCl₄

adds 2 X’s to either end of alkyne forming an alkane 

adds 4 X’s in total 

1 eq HX and CCl₄

adds 1 X to either side of alkyne forming an alkene

forms both E and Z isomers of alkene

adds 2 X’s in total

O₃ on internal

forms 2 carboxylic acids

keeps main chain from either side of alkyne to one of each carboxylic acids

cuts double bond

O₃ on terminal

forms one carboxylic acid and one CO₂

keeps main chain on the carboxylic acid

cuts double bond

ketone with two OH groups automatically degrades into CO₂

NaNH₂ and alkyl group w/ halide (RX)

addition of alkyl chain to terminal alkyne

acetylene can add 2 alkyl chains to either side

halide must be on primary position to add alkyl groups to alkyne

formation of internal alkyne

E2 is performed twice

NaNH₂ deprotonates twice from 2 leaving groups

one-step reaction

formation of terminal alkyne

E2 is performed twice

NaNH₂ deprotonates twice from 2 leaving groups but also deprotonates acidic H

quenching step (H₂O) adds H back to alkyne