4. We separated Carvone and limonene from spearmint oil, by micro column chromat

Question

4. We separated Carvone and limonene from spearmint oil, by micro column chromatography with silica gel and an eluotropic series of hexanes and acetone. If you start adding hexane, which compound, limonene or carvone, do you expect would elute first from the silica gel micro column?
Discuss the validity of the following statements:

a) A mixture of (+)- and (-)-carvone can be separated by column chromatography on silica gel using hexanes-acetone as elution solvent.
b) In general, column chromatography on silica gel is run with a series of solvents on increasing polarity.
c) Carvone is more polar than limonen

Explanation / Answer

column chromatography will work on absorptin principal

if the compound is more polar it will stick more with silica the moment will be slow

where as if compound is less polar it will stick less to the silica gel means it will move quickly in column

A)

a mixture of (+) and (-) carvon can not separate in column chromatography

because both are enetiomers enantomers cannot separable in column chromato graphy only diastereomers can be separablew in column because diastereomers can have different physical properties where as enantomers will have same physical properties except their rotation of plane polarised light.

b)

yes you need to run like this then first less polar compound will come with lower polarity of solvent mixture

then if you keep increasing the polarity then hipolarity compounds will come as shown in the above

c)

yes Carvon is more polar than limonene because carvone is having unsturated eater that group will be polar because double bond will conjugate with ketone group so hole molecule is polar compare to liminone

whaereas limenione is only having isolated double bonds those are less polar than conjugated double bond

if run the column at lower polarity liminone will come first and at higher polarity carvonw will come.

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