6. Cis 1,3 dimethyl cyclohexane is optically inactive because -
(a) It has a plane of symmetry. (b) It has a centre of symmetry.
(c) There is no chiral centre.
(d) There are two 1,3 diaxial interactions.
7. Trans 1,3 dimethyl cyclohexane is optically active because –
(a) There is no plane of symmetry
(b) Two chiral centers are different.
(c) The enontiomers have equal stability. (d) There are no butane gauche interactions
8. The order of stability of 1,4 dimethyl cyclohexane is -
(a) Trans 1,4 (e,e) > cis 1,4 (a,e) > trans 1,4 (a,a):
(b) Trans 1,4 (a,a) > trans 1,4 (e,e) > cis 1,4 (a,e).
(c) cis 1,4 (a,e) > trans 1,4 (aa) > trans 1,4 (e,e).
(d) cis 1,3 (e,a) = trans 1,4 (a,a) = trans 1,4 (e,e).
Answers
Answer:
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Explanation:
6. Option (a) It has plane of symmetry.
A molecule is said to be chiral when it possess a chiral center, does not has a plane of symmetry, or a center of symmetry.
Here, the molecule Cis 1,3-dimethyl cyclohexane can be divided into two similar halves because it has a plane of symmetry which makes it an optically inactive molecule.
7. Option (a) There is no plane of symmetry.
The molecule Trans 1,3 dimethyl cyclohexane is optically active and can rotate the plane of plane polarized light. This property is due to the absence of plane of symmetry.
When we divide this molecule into two halves, we do not get similar halves due to the changed orientation of both methyl groups as they are in trans position.
8. Option (b) Trans 1,4 (a,a) > trans 1,4 (e,e) > cis 1,4 (a,e).
Among cis and trans form of a molecule, trans is more stable than cis form due to the structural stability.
In cis form, both groups are present on same side, which creates stearic hindrance and lowers the stability of molecule.
In trans form, both groups are present on opposite sides that decreases the overall energy and increase the stability of molecule.