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The suffix ‘Mers’ comes from a greek term Meros meaning ‘parts’ or ‘shares’. And it has been used a lot in classification for convenience. One very wide usage of this suffix is found in Organic Chemistry. In this context, it refers to ‘Repeat Units’ of x; x depending on the how it is used such as in isomers, homomers, enantiomers, homopolymers & copolymers.

But this is less about the suffix ‘Mers’ and more about the confusion it has(/might) created(/create). Even during my JEE preparations, there were times we were haunted by such confusion, so it’s perfectly alright. What’s not alright is not attending to your doubt and leaving it unclosed to haunt you during exams. Now since this can be avoided, we decided to take these words up for discussion – Homomers, Enantiomers, homopolymers & copolymers.

Enantiomers vs Diastereomers vs Meso Compounds

Both Enantiomers & Diastereomers are optical isomers of the same compound. But there’s a small difference between the two. So small that this amounts to confusion at times. Let’s look at these through an example.

A & B are Enantiomers of each other if they have the same molecular structure, there is a chiral carbon present & they are non-superimposable mirror images of each other.

enantiomers
Enantiomers

A & B are Diastereomers of each other if they have the same molecular structure, there is a chiral carbon present & they are not the mirror images of each other.

A is a Meso Compound if it has a mirror image superimposable on it. At least one carbon has asymmetric bonds but the carbon is not chiral due to the presence of symmetry such that a plane will bisect the compound in two equally identical parts (Mers!) Due to the rendering of the asymmetric carbon as achiral, Meso compound is optically inactive.

Meso Compound
Meso Compound

Hoping this difference is clarified, let’s move on to another popular confusion.

Homomers vs Homopolymers

It is understandable why these two terms are causing confusion to the aspirants. But, these belong two very much different areas of Organic Chemistry. Let’s take a look.

Homopolymers are polymers which are a result of polymerisation between the same compounds. For example Polythene or Poly-ethylene or (CH2CH-)n– is a homopolymer.

Homomers do not belong to polymerisation. Rather they belong to isomerism. There are times when same compound is represented in two different forms that might lead to believing that the representations are of two different compounds; these two different representations are called homomers.

Homomers
An example of Homomers

In the example above, both the compounds are exactly same (yes, not even optical isomers). They are just represented differently (to confuse many times).

Homo-Polymers vs Co-Polymers

These are more or less clear to most. But, there still is some confusion. But this one’s fairly simple.

Both homo-polymers & co-polymers are a result of polymerisation. But, homopolymers are a result of polymerisation between same compounds while co-polymers are a result of polymerisation between two or more different compounds.

PolyEthylene
Poly-Ethylene – A Homopolymer
Copolymer
Copolymer of Lactic Acid & Glycolic Acid

These are some very common confusions. We hope this article help these sort out. If you want us to clear up any other topics you may share in the comments’ section. For more interesting reads & important updates click here

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