Advices For Studying Organic Chemistry

CC+ X

X

Y CC

Y

A syn addition

2. Anti addition:

CC+ X

X

Y CC

Y

A anti addition

7.15 HYDROGENATION OF ALKYNES

1. Depending on the conditions and the catalyst employed, one or two molar
   equivalents of hydrogen will add to a carbon–carbon triple bond.

1. A platinum catalyst catalyzes the reaction of an alkyne with two molar
   equivalents of hydrogen to give an alkane.

CH 3 C≡CCH (^3) HPt [CH 3 CH=CHCH 3 ] Pt CH 3 CH 2 CH 2 CH 3
2 H 2

7.15A SYN ADDITION OF HYDROGEN: SYNTHESIS OF CIS-ALKENES

1. A catalyst that permits hydrogenation of an alkyne to an alkene is the nickel
   boride compound called P-2 catalyst.

OCCH 3

O

Ni

NaBH 4

(^2) C 2 H 5 OH NiP-2^2 B

1. Hydrogenation of alkynes in the presence of P-2 catalyst causes syn addition of
   hydrogen to take place, and the alkene that is formed from an alkyne with an
   internal triple bond has the (Z) or cis configuration.


2. The reaction take place on the surface of the catalyst accounting for the syn