IIT JEE , AIEEE Forum - Chemistry , Organic Chemistry - diff. b/w metamers and position isomers ?

umang

pls explain

rabindra8

isomers which differs in position of any atom or group including c=c and carbon carbon triple bond.are called as position isomers.

e.g. 2-methylpentane.and 3-methylpentane. this is position isomers only.

isomers which differs in number of carbon atom on either side of functional group are called as metamers.

e.g. methoxy propane and ethanoxy ethane. this is metamers and also position isomers ,

metamers are always position isomers but position isomers may or may not be metamers.

it's clear now .then rate me.

umang

yes , that was my doubt -
are metamers always position isomers ???
r u sure about it bcoz I read it somewhere that it is not so .
pls confirm !

waterdemon

Position Isomers:
The Compounds having same molecular formula but different
positions of Double Bond,Triple Bond or Functional Group are
"Position Isomers" of each other.

Eg:
(1)CH₃-CH₂-CH=CH₂ (1-Butene)
   CH₃-CH=CH-CH₃ (2-Butene)

(2)CH₃-CH₂-CH₂-OH (Propanol-1)
   CH₃ - CH - CH₃   (Propanol-2)
            l
   OH

Metamerism:
Compounds having same molecular formula but different no.
of Carbon atoms(Alkyl Group) on either side of functional
group are called as "Metamers".

Usually metamerism is observed in Ether,Ketones,ester,2⁰
and 3⁰ amines where alkyl groups are attached to same
functional group.

Eg:
(1)CH₃-CH₂-OCH₂-CH₃ (Ethoxy ethane)
   CH₃-O-CH₂-CH₂-CH₃ (1-methoxypropane)
   CH₃-O-CH-CH₃        (2-methoxypropane)
              l
            CH₃

And Metamers may also be Position isomers.
For example: "pentanone-2" and "pentanone-3" are both
               position isomers and metamers.

Hope it is useful.
Rate if useful.

Cheers!!!!!@@!!!!!!

umang

Hey waterdemon !
just one more doubt -
can I call hex-2-ene and hex-3-ene metamers ?
Thanks !!

waterdemon

No,
Pentanone-2 and pentanone-3 are metamers as well as they
are position isomers as they have the functional group at
different positions.

But Hex-2-ene and Hex-3-ene are only Position Isomers &
not Metamers as there is no change in the position of the
Functional group which I know is not present.

Hope you find it useful.
Rate if useful.

Cheers!!!!!@@@!!!!!!

umang

Thanks a lot for helping !

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