Organic Chemistry

retinol

vitamin A

I

n this chapter,

we will look at the

reactions of compounds

that have two double bonds. Hydrocarbons

with two double bonds are called dienes, and

those with three double bonds are called trienes. Tetraeneshave four double bonds,

and polyeneshave many double bonds. Although we will be concerned mainly with

the reactions of dienes, the same considerations apply to hydrocarbons that contain

more than two double bonds.

Double bonds can be conjugated,isolated, or cumulated. Conjugated double

bondsare separated by one single bond. Isolated double bondsare separated by more

than one single bond. In other words, the double bonds are isolated from each other.

Cumulated double bondsare adjacent to each other. Compounds with cumulated

double bonds are called allenes.

-cadinene

oil of citronella

a diene

zingiberene

oil of ginger

a triene

• selinene
  oil of celery
  a diene


• carotene
  a polyene

298

8

Reactions of Dienes •

Ultraviolet and Visible

Spectroscopy