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1. SYNTHESIS OF BENZOPINACOL FROM
BENZOPHENONE BY PHOTOREDUCTION AND ITS
INFRARED SPECTRUM CHARCTERIZATION
Submitted by
LOKESHKUMAR C
Register Number: 561930036
Under the guidance of
Mrs.C.SELVINTHANUJA,M.Pharm.,
Assistant Professor,
Department of Pharmaceutical Chemistry.
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2. Photochemistry is the study of chemical reaction that occur by absorption of light
radiation.
TYPES
•Photo-dissociation: AB + hν → A* + B*
•Photo induced rearrangements, isomerization: A + hν → B.
•Photo-Addition: A + B + hν → AB + C.
•Photo-substitution: A + BC + hν → AB + C.
•Photo-redox reaction: A + B + hν → A− + B+
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3. REACTION
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PROCEDURE
2g Benzophenone + 10ml 2-propanol + 1drop glacial acetic acid were
placed in 20ml vial and closed with aluminium foil followed by closed with
rubber. Then vial was exposed with direct sunlight for 5 days. The crystals of
benzopinacol was formed and it was scraped and dried.
hv

4. 4
MECHANISM Step:1
Step:2 Step:3 Step:4
hv

5. CHARACTERIZATION
Practical yield=2.06g
Melting point=174-180℃
NITROGEN RULE
Nitrogen rule in mass spectrometry states that the organic molecule that contain even number of
nitrogen atoms or No nitrogen atoms will have even molecular mass, where as molecule that
contain an odd number of nitrogen atoms will have odd molecular mass.
Eg:
Benzophenone Benzopinacol
C=12x13=156. C=12x26=312.
H=1x 10 =10. H= 22x1 =22.
O=1x16 =16. O=16x2 =32.
Total-182(even). Total-366(even).
Molecular mass of benzopinacol is 366. As per nitrogen rule, it does not contain nitrogen and
even molecular mass.
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DOUBLE BOND EQUIVALENT
DBE is used to find number of double bond and number of triple bond present in organic
molecule.
DBE=C+1-H/2-X/2+N/2
C=Carbon
H=Hydrogen
X=Halogen
N=Nitrogen
Eg: Benzophenone (C13H10O)
DBE=13+1-10/2-0/2+0/2
=14-10/2
=9 { No of double bond =7 + No of ring =2 } Add=9
Benzopinacol (C26H22O2)
DBE=26+1-22/2-0/2+0/2
=27-22/2
=16 { No of double bond =12 + No of ring =4 } Add=16

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TLC
TLC was performed to check the purity of benzopinacol using the mobile phase
isopropanol and water in the ratio of 7:3 and silica gel coated plate as stationary phase.
Distance travelled by center of compound
Rf=
Distance travelled by solvent font
Benzophenone: Rf=3.6 / 5.4=0.66
Benzopinacol: Rf=3.1 / 5.4=0.57

8. SPECTAL ANALYSIS
UV - It is a analytical technique that measure the amount of wavelength of UV or
visible light that are absorbed by sample or transmitted through a sample in comparison to
reference or blank sample.
Normal range=200-400nm
λmax of benzopinacol=248nm
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IR
It used to measures the vibrational spectrum of a sample by passing IR
radiation. It help to determine the functional group of the compound.. Most of the bands
that indicate what functional group is present are found in the region from 4000 cm-1 to
1300 cm-1.
In Benzophenone Ar-Keton (C=O) at (1650.95) are convert to Benzopinacol Two alcohol
(OH) at (3573.85 &3544.92) stretching was observed.

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