How can I draw 3–methylpent–2–ene, (CH_3CH = C(CH_3) CH_2CH_3), and know if it shows E-Z isomerism?

1 Answer
Ernest Z.
Aug 24, 2015

First you expand the condensed structural formula to a bond-line view, and then you check whether there are two different groups on each end of the "C=C" bond.

Explanation:

Step 1. Draw the bond-line structure.

opsin.ch.cam.ac.uk

Step 2. Check for two different substituents on each end.

In the structure above, the left hand "C" atom has an "H" and a "CH"_3 (two different substituents).

The right hand end has a "CH"_3 and a "CH"_2"CH"_3 (two different substituents).

The compound shows E"/"Z isomerism.

In the above structure, the "CH"_3 group on the left hand end has priority 1, while the "CH"_2"CH"_3 group on the right hand end has priority 1.

Since the two high-priority groups are on opposite sides of the double bond, the compound is (E)-3-methylpent-2-ene.

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