Advices For Studying Organic Chemistry

with three double bonds have the general formula CnH2n–4.

CH 2 =CH–CH=CH 2 CH 2 =CH–CH=CH–CH=CH 2
1,3-Butadiene (C 4 H 6 ) 1,3,5-Hexatriene (C 6 H 8 )

3. Index of Hydrogen Deficiency (degree of unsaturation, the number of
   double-bond equivalence):

1. It is an important information about its structure for an unknown compound.


2. The index of hydrogen deficiency is defined as the number of pair of hydrogen
   atoms that must be subtracted from the molecular formula of the corresponding
   alkane to give the molecular formula of the compound under consideration.


3. The index of hydrogen deficiency of 1-hexene and cyclohexane:
   C 6 H 14 = formula of corresponding alkane (hexane)
   C 6 H 12 = formula of compound (1-hexene and cyclohexane)
   H 2 = difference = 1 pair of hydrogen atoms
   Index of hydrogen deficiency = 1

4. Determination of the number of rings:
   
   
   1. Each double bond consumes one molar equivalent of hydrogen; each triple bond
      consumes two.
   
   
   2. Rings are not affected by hydrogenation at room temperature.
   
   
   
   

CH 2 =CH(CH 2 ) 3 CH 3 + H 2 25 PotC CH 3 (CH 2 ) 4 CH 3

+ H 2 25 PotC No reaction

+ H 2 25 PotC

Cyclohexene

CH 2 =CHCH=CHCH 2 CH 3 + 2 H 2 25 PotC CH 3 (CH 2 ) 4 CH 3
1,3-Hexadiene