In: Chemistry
How many configurational isomers are possible for the following compounds?
A. 4-chloro-3-hexen-2-ol
B. 2,4-hexadiene
C. 3-chloro-1,4-pentadiene
Answer: There are far too many to do all three
for you, but the general approach is "be methodical". Draw the
structural skeletal formula for the starting substance, then work
at moving the important features (the double bonds) to other
locations. Once all positions for the hexadienes have been located,
remove an end carbon (a methyl) and begin placing it as an interior
carbon substitution on the patterns already generated (where the
double bonds are moved to different locations. These will all be
methylpentadienes. After that, do the dimethylbutadienes.
For example, starting with the hexadienes you can write 1,2; 1,3;
1,4; and 1,5 hexadienes then 2,3; 2,4; 2,5 hexadienes followed by
3,4; and 3,5 hexadienes and finally 4,5 hexadiene - that gives us
10 isomers for hexadienes.
For the methylpentadienes we can write: 2-methyl-1, 3-pentadiene;
2-methyl-1, 4...; 3-methyl-1, 3...
3-methyl-1, 4...; 4-methyl-1, 3...;4-methyl-1, 2...;and 4-methyl-1,
4pentidiene thats 7 more isomers
Finally there is one dimethylbutadiene:
2,3-dimethyl-1,4-butadiene
The total is 18 isomers for the first one only.
If you'll sit down and write out each of these iosmers in the order
presented you'll see what "be methodical" means. I use skeletal
formulas when I'm planning like:
C=C=C-C-C-C and C=C-C=C-C-C and C=C-C-C=C-C and C=C-C-C-C=C
or.. C
.....|
C=C-C-C=C