Advices For Studying Organic Chemistry

General Reaction

R X

X X

++Zn HX R H + ZnX 2

R (Zn, −ZnXH R H

2 )

or*

1) *Abbreviated equations for organic chemical reactions:

i) The organic reactant is shown on the left and the organic product on the right.

ii) The reagents necessary to bring about the transformation are written over (or

under) the arrow.

iii) The equations are often left unbalanced, and sometimes by-products (in this

case, ZnX 2 ) are either omitted or are placed under the arrow in parentheses

with a minus sign, for example, (–ZnX 2 ).

Specific Examples

(^2) Zn 2CH 3 CH 2 CHCH 3
H
Br ZnBr 2
Br

• sec-Butyl bromide
  (2-bromobutane)
  Butane
  CH H
  3 CH 2 CHCH 3
  2 CH 3 CHCH 2 CH 2 2 +
  Isopentyl bromide
  CH 3
  Br
  Br Br
  Zn^2
  H CH
  3 CHCH 2 CH 2
  CH 3
  H
  (1-bromo-3-methylbutane)
  Isopentane
  (2-methylbutane)
  Zn

2. The reaction is a reduction of alkyl halide: zinc atoms transfer electrons to the
   carbon atom of the alkyl halide.

1. Zinc is a good reducing agent.


2. The possible mechanism for the reaction is that an alkylzinc halide forms first
   and then reacts with the acid to produce the alkane: