A Structure Recognition Problem

Problem 1.
Examine the following formulas and select those pairs that satisfy the following conditions:
Be sure to enter two letters (and only two) in each answer box, unless you select F. In the second and third parts more than one answer is possible.

A

B

C

D

E

F No formulas meet the designated condition.

Which are identical in all respects? ...
Which are conformational isomers? ..
Which are constitutional isomers? ....

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Problem 2.
Examine the following formulas and select those pairs that satisfy the following conditions:
Be sure to enter two letters (and only two) in each answer box. In the second and fourth parts more than one answer is possible.

A

B

C

D

E

F

Which are identical in all respects? ....
Which are configurational isomers? ...
Which are conformational isomers? ...
Which are constitutional isomers? .....