Question

Draw the structure of (Z)-3-methyl-3-heptene. Be sure the stereochemistry is drawn clearly.

Answer 1

As name ends with heptene it means a parent alkane from which name if derived is heptane i.e. longest chain is of 7 C atoms. So straight long chain of 7 C atoms is drawn and C atoms are numbered from 1 to 7.

3-heptene (hept-3ene) indicate that C=C is between C3 and C4 atom and hence drawn accordingly.

3-Methyl is substituent at C3 as 3-indicates its locant number.

Stereochemisty i.e Geometry: (Z) geometrical isomer asked to draw. Prefix (Z) means same priority groups are on same side of the axis passing along C=C.

C3 has -CH3 and -CH2CH3 groupings and -CH2-CH3 prior over -CH3

and C4 has -H and -CH2-CH2CH3 groupings and -CH2-CH2-CH3 prior over -H..(Cahn-Ingold-Prelog rules followed)

i.e -CH2-CH3 and -CH2-CH2-CH3 are equally prior groups separately on C3 and C4 respectiveli and they are shown on same side of axis passing through C=C.

Hence the structure of (Z)-3-Methyl-3-heptene.

axis 2 CH H2C- 7 H2 (Z)-3-methyl-3-heptene