cis and trans isomers - chemistry (11.17 module 11)

Question

I have attached questions to each statement as to why they are wrong and right.

Which statement about isomerism is correct?

A. In cis/trans isomerism with respect to a double bond, the nature of the atoms attached to the double bond on each C atom doesn't matter. - explain to me what they mean by "nature of the atom"

B. Function isomers differ from each other by the location of the functional group.

- what is function isomer?

C. In enantiomers, the molecules are characterized by a plane of symmetry. - what do they mean by plane of symmetry?

D. (correct answer) Optical isomers are not always each other's mirror image. - why is this correct? I thought that optical isomers are a mirror image of each other, in what case is it not?

Answer 1

A. I'm not sure for what they mean by the "nature of the atom", but CIS means you have two similar groups on the same side of the double bond. TRANS means you have them on opposite sides.

B. Functional or Structural isomers have the same molecular formula, but different structures... The atoms are connected in a different order.

C. Enantiomers are mirror images of each other. They do not have a plane of symmetry. Meso compounds have a plane of symmetry. A plane of symmetry can be googled for the definition. Basically, it divides two halves of an object into identical parts or regions.

D. Optical isomers can be two diastereomers which are not mirror images of each other.