Alkyne Reaction Mechanisms

Alkylation

1. NaNH2

2. R'-X

X= Cl, Br, I

Poisoned Hydrogenation

CIS

1. H2

2. Lindlar's Cat

ends at alkene product

sun addition= cis alkene

Catalytic Hydrogenation

1. H2

2. Pt

forms alkane

syn addition

not selective

Dissolving Metal Reduction

TRANS

Synthesis:

1) Na,

2) NH3 [liquid]

anti addition

trans alkene only

part polar part rad

Hydrohalogenation POLAR

1. HBr but also HCl in xs

MARK

Hydrohalogenation RADICAL

1. HBr

2. ROOR

xsHBr

ROOR

anti mark

Halogenation

1. X2 (br or cl)

2. CCl4

xsX2

CCl4

-Reagents: Br2 or Cl2 in CCl4

-Addition

-First addition is usually trans

-Markovnikov addition

-Excess X2 ---> tetrahalides

Acid Catalyzed Hydration

1.H2SO4, H2O

2. HgSO4

goes through enroll which is where OH single bond becomes O double bond

MARK= H least OH most

enol: C=C becomes C=O (Me Ketone)

tautamerization

constitutional isomers

Hydroboration-Oxidation

1. BH3, THF

2. H2O2, NaOH

1. BH3, THF

2. H2O2, NaOH

forms aldehyde (vs AC hydration which forms ketone)

ANTIMARK= H most and OH least

enol is formed goes through ketone/enol tautamerisation

ozonolysis (terminal alkyne)

1. O3, DMS

2. H2O

1CO2 forms with 1carbox acid

R3H

ozonolysis (internal alkyne)

1. O3, DMS

2. H2O

2 carboxylic acids form

R3R'

2 carboxylic acids form