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Chemical physical Spectroscopic and
spectrometer structure elucidation of
terpenoids
Method used for structural elucidation of
terpenoids are quite similar to that of
Alkaloids
...
invariably
terpenoids Contains carbon hydrogen
and most of it contains oxygen
...
Determination of molecular
weight finally leads to molecular formula
...
In our modern
day practice it is done by mass

spectrometry,in which the signals due to
molecular ion M+ ion are identified
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3-Determination of functional groups
(a)Functional nature of oxygen
>Hydroxyl group
The presence of -OH group is checked by
the action of acetic acid ,acetyl chloride or
benzyl chloride on terpenoids
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The
next problem is to decide whether the
-OH group is Alcoholic or Phenolic
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Also chlorination with
FeCl3 indicates the presence of Phenolic
group
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Nature of an
alcoholic group that is prim
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or ter
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Primary alcohols and oxidation yields
Aldehyde ,secondary alcohols yields
ketones and Tertiary alcohols give
elimination reactions
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Oxo group:
The presence of the oxo group is readily
checked by formation of OXime ,
Semicarbazone, and Phenylhydrazone
...

+ HI
CH3I +AgNO3

ROH + CH3I
AgI +CH3NO3

The terpenoid is heated with concentrated
hydrochloric acid(HI) at its boiling point
(126);The Methoxy, group is converted
into methyl iodide ,Which is then
absorbed by Silver Nitrate(AgNO3) and
precipitate of silver iodide(AgI) are weight
out
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>Methylenedioxy group Presence of this
group is indicated by formation of
formaldehyde when heated with HCl/
H2SO4
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Depending on how many moles of H2 OR
Br2 are used we can suggest how many
double bonds are present in a particular
Terpenoids
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(d)Aromaticity of alkaloids The cyclic
compounds are subjected to
Westerbergs dehydrogenation ,with
S/Se/ Pd at high temperature to check the
aromaticity of a compound
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UV Spectra are used to indicate likely
type of structure /conjugation in a
compound
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(f)Synthesis
The foregoing Analytical work will
ultimately lead to the proposal for
tentative structures for the terpenoids
under consideration
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