O chem Question

[luv8724]

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Is this meso compound?

cis-1-chloro-4-methyl cyclohexane

or to be a meso.. does both of the substituents have to have chiral centers?

 

[orgohacks]

Is this meso compound?

cis-1-chloro-4-methyl cyclohexane

or to be a meso.. does both of the substituents have to have chiral centers?

In this instance, no. Like a meso compound you have an internal mirror plane but you don't have chiral centers.

Generally speaking you have a meso compound when toggling the stereochemistry of one of the chiral centers would give you a chiral compound.
For instance meso tartaric acid (R,S) becomes chiral if you toggle either stereocenter (i.e. R,R or S,S).

 

[CANgnome]

so it is not meso even though it has a plane of symmetry because it has no chiral carbons?

 

[orgohacks]

so it is not meso even though it has a plane of symmetry because it has no chiral carbons?

Right - it's not meso.

Kind of a semantic issue though. Whatever you want to call it, it's achiral.

Meso is kind of an old fashioned term from the early 1900s. For instance, the two enantiomers of tartaric acid rotated polarized light to the left and to the right. Then there was a third stereoisomer of tartaric acid which didn't rotate polarized light at all. This was called the "meso" isomer (middle) for this reason.