Chemistry - STEREO ISOMERISM Question with Solution | TestHub

Ans. 4

Sol. 1 sp carbon i.e., 1C connected with 2 pi-bonds; 2 sp² carbon i.e., 2C connected with 1 pi bond each; 2 sp³ carbon i.e., 2C connected with only sigma bonds. The only carbon skeleton fitting this is a cumulated diene (allene), C=C=C. Possible structures are -

+ enantiomer = 2

= 1

= 1

Penta-2,3-diene has different groups (H and CH₃) on both terminal allene carbons, so it is axially chiral and exists as an enantiomeric pair (2); 3-methylbuta-1,2-diene and penta-1,2-diene each have two identical groups on one terminal carbon, so they are achiral (1 each).

Total = 2 + 1 + 1 = 4