Advices For Studying Organic Chemistry

CH 3 CHC CH

CH 3

CH 3 CHC C

CH 3

−Na+ CH^3 Br CH 3 CHC C

CH 3

CH 3

CH 3 CHCH 2 CH 2 CH 3

CH 3

NaNH 2

(−NH 3 ) (−NaBr)

excess H 2 Pt

4.19 SOME GENERAL PRINCIPLES OF STRUCTURE AND

REACTIVITY: A LOOK TOWARD SYNTHESIS

1. Structure and reactivity:
   
   
   1. Preparation of the alkynide anion involves simple Brønsted-Lowry acid-base
      chemistry.
      i) The acetylenic hydrogen is weakly acidic (pKa ~ 25) and can be removed with
      a strong base.
   
   
   2. The alkynide anion is a Lewis base and reacts with the alkyl halide (as an
      electron pair acceptor, a Lewis acid).
      i) The alkynide anion is a nucleophile which is a reagent that seeks positive
      charge.
      ii) The alkyl halide is a electrophile which is a reagent that seeks negative
      charge.
   
   
   
   

Figure 4.25 The reaction of ethynide (acetylide) anion and chloromethane.
Electrostatic potential maps illustrate the complementary nucleophilic
and electrophilic character of the alkynide anion and the alkyl halide.