Question

Name the following compounds???

Answer 1

a. (`Z`)-but-2-ene; b. buta-1,3-diene; c. (`E`)-pent-2-ene.

Explanation:

`bb"4a"`

1. Count the carbons. This is a four-carbon alkene (a butene).
2. Number the carbons. Give an alkene carbon the lowest number (2).
3. Name the alkene. Put the "2" immediately before the "ene" and separated from the letters by hyphens (but-2-ene).
4. Assign stereochemistry. The lowest priority groups (`"H"`) are on the same side of the double bond. The compound is (`Z`)-but-2-ene.

`bb"4b"`

1. Count the carbons. This is a four-carbon alkene with two double bonds. Insert the multiplying prefix di before the "ene" (butadiene).
2. Number the carbons. Give the alkene carbons the lowest possible numbers
   (1 and 3).
3. Name the alkene. Put the insert the numbers, separated by a comma, immediately before the "diene" and separated from the letters by hyphens. The compound is buta-1,3-diene.

`bb"4c"`

1. Count the carbons. This is a five-carbon alkene (a pentene).
2. Number the carbons starting from the end closest to an alkene carbon.
3. Name the alkene. Put the "2" immediately before the "ene" and separated from the letters by hyphens (pent-2-ene).
4. Assign stereochemistry. The lowest priority groups (`"H"`) are on opposite sides of the double bond. The compound is (`E`)-pent-2-ene.