Question

How many and what are the isomers of `C_4H_8`?

Answer 1

A formula of `C_4H_8` specifies 1 degree of unsaturation.

Explanation:

One degree of unsaturation involves the presence of an unsaturated bond OR a ring.

So I can count 5 structural isomers: 2 rings, and 3 olefins. One of the olefins has 2 geometric isomers.

As regards the degree of unsaturation, this is a useful reference when we compare the formula to a saturated molecule, `C_nH_(2n+2)`, i.e. butane if `n` `=` `4`. How many isomers can butane, `C_4H_10`, generate?

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