11 Say true or false a. In some cases, constitutional isomers are chiral. b. In

Question

11 Say true or false a. In some cases, constitutional isomers are chiral. b. In every case, a pair of enantiomers have a mirror-image relationship. c. Mirror-image molecules are in all cases enantiomers d. If a compound has an enantiomer, it must be chiral. e. Every chiral compound has a diastereomer. f. If a compound has a diastereomer, it must be chiral. g. Every molecule containing one or more asymmetric carbons is chiral. h. Any molecule containing a stereocenter must be chiral. i. Any molecule with a stereocenter must have a stereoisomer j. Some diastereomers have a mirror-image relationship Some chiral compounds are optically inactive. I. Any chiral compound with a single asymmetric carbon must have a positive optical rotation if the compound has the R configuration. m. A structure is chiral if it has no plane of symmetry n. All chiral molecules have no plane of symmetry o. All asymmetric carbons are stereocenters SH

Explanation / Answer

(a) Yes.

Reason: Consider the example of (a) 1,2 dichloropropane and (b) 2,2 dichloropropane. a and b are constituitional isomers.

b is achiral and its constituitonal isomer a is chiral. The above example substantiate the question.

b) Yes

Reason: Non-superimposable mirror images are called enantiomers

c) No

Reason: There can be mirror images that are superimposable and only non-superimposable mirror images are called enantiomers For example, meso compunds like meso tartaric acid.

d) Yes

Reason: non-superimposable mirror images are called enantiomers. if they are non-superimposable they must be chiral

e) No.

Reason: A minimum of 2 chiral center is requred for the compound to be eligible to possess a diastereomer. In some cases even constituitional isomers can be diastereomeric.

F) No.

Reason: Meso compouds are achiral however, they have distereomeric relationship with their their optically active counterparts. Eg. Meso tartaric acid and L tartaric acid are diastereomers

g) No.

Reason: Meso compounds having many asymmetric carbon atoms are achiral due to plane of symmetry.

h. No.

Reason: compounds which has a plane of symmetry are not chiral even though they have stereo centers. Eg. Meso tartaric acid

i) Yes.

Reason: Compouds containing stereocenters have their mirror images as isomers.

j) No.

Reason: The very definition of diastereomers itself contradict the statement. Diastereomers are the optical isomers devoid of mirror image relationship.  

k) No.

Reason: Chiral compounds doesnt have plane of symmetry and center of symmetry in general. Therefore they are optically active.

l) No.

Reason: Optical rotatory power is the intrinsic and innate capacity of a chiral molecule. It is experimentally determined. However, R and S configuration is rationally assigned to a chiral center to showcase the attachment of groups around the carbon in 3 dimension.

m) No

Reason: even if it does not possess plane of symmetry, other symmetries like point of symmetry can make the molecule aciral.

n) Yes

Reason: if it has plane of symmetry, one half of the molecule will be the exact half of the other half and the molecule cannot be chiral

o) Yes

Reason: Asymmetric carbon are those attached with different groups to complete its valency. Since all groups are different, interchanging any two groups can result in forming a stereoisomer (condition for becoming a stereocentre)

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