Ch.13: Alkynes

Question 1

Strong Bases to use for rxns

Answer 1

Alkyl lithium, grignard reagents, NaNH2 in liquid NH3, LDA

Question 2

E2 of Dihaloalkanes

Answer 2

Rxn conditions: (CH3)3COK in DMSO or a strong base and H2O
Products: Triple bond along the dehalogenated carbons

Question 3

Alkylation of Alkynl Anions

Answer 3

Rxn conditions: Alkyl lithium or grignard reagent and a base for first step, then SN2 occurs on the lone pair on the triple bond

Question 4

Electrophilic Addition of HX

Answer 4

Rxn conditions: HBr
Syn Addition
Product: Haloalkene if occurs once, dihaloalkene if occurs twice

Question 5

Electrophilic Addition of X2

Answer 5

Rxn conditions: Br2 with acetic acid and LiBr, or with CCl4
Occurs twice for complete hydrogenation, two halogens on each carbon of the bond
Products: 1,2-dihaloalkane

Question 6

Oxymercuration

Answer 6

Rxn conditions: Terminal alkyne, H2O + HgSO4
Product: Enol
The enol then undergoes tautomerization to produce a ketone
Final Product: Ketone

Question 7

Radical HBr

Answer 7

Rxn conditions: HBr and peroxides
Anti-Markovnikov
Product: Haloalkene

Question 8

Hydroboration-Oxidation

Answer 8

Rxn conditions: HBr first step then peroxide and hydroxide ion second step
Bulky group must be used to ensure single hydroboration
Product: Enol that tautomerizes to an aldehyde or ketone