M.Sc. (Semester III) (CBCS) Examination Nov/Dec-2018
Organic Chemistry
ADVANCED SPECTROSCOPIC METHODS
Time: 2½ Hours
Max. Marks: 70
Instructions: Answer to all questions should be written in one answer book. All questions carry equal marks. Figures to the right indicate full marks. Use of log table and calculator is allowed.
Q.1

Answer the following
09
The CMR spectrum of an unknown compound shows 5 absorptions and the PMR spectrum shows 5 absorptions. Which of the following compound is the unknown compound?




HETCOR spectra is used to detect directly bonded.
13C-1H
13C-13C
1H-1H
None of the above
Which of the following transitions is the highest energy transition?

σ−σ*


How many Hertz does 1 ppm correspond to for PMR spectrometer operating at a radiofrequency of 60 MHz and 100 MHz?
100 Hz, 60 Hz
60 Hz, 100 Hz
90 Hz, 150 Hz
6 Hz, 10HZ
Which of the following bonds would show the strongest absorption in the IR?
O-H
N-H
S-H
C-H
The force constant of a C=C bond is than that for a C-C bond, and its peak occurs at a frequency in the IR spectrum.
smaller, lower
larger, lower
smaller, higher
larger, higher
DEPT
Distortion less enhancement polarisation technique
Distortion less enhancement polarisation transfer
Different enhancement polarisation transfer
All above
19F and 31P have nuclear spin equal to
1/2
1
5/2
3/2
How many lines do you expect to see in the 1H NMR spectrum for the following molecule?
2
3
4
10
b)Give answer of the following.
05
What do you mean by Coupling constant?
What is base peak in mass spectrum?
Which of the following diatomic molecules don't absorb in the IR region?
HCl, HBr, ClBr, Cl2, H2, Br2
How many signals are possible in the 13C NMR spectrum of following compounds?
COOHOMeCOOHand
What is Nitrogen Rule?
Q.2
a)Answer the following (Any Four)
08
Arrange the following compounds in order to their increasing wave number of absorption due to stretching in the following compounds.
OOOOOOIIIIII
How will you distinguish between cis and trans isomers of cinnamic acid by PMR?
What is AB and AX spin notation?
Why ethyl benzene exhibits a strong peak at
Define first order and second spectra?
b)Answer the following (Any two)
06
McLafferty rearrangement
Anisotropy effect
DEPT technique of NMR
Q.3
a)Answer the following(Any two)
08
Describe A2B2 and A2X2 spin systems with examples?
Explain different factors affecting on IR stretching frequency?
Distinguish between following compounds by 1H NMR technique
b)Answer he following (Any one)
06
Explain different modes of fragmentation in mass spectroscopy?
Discuss HETCOR and COSY techniques in NMR?
Q.4
a)Answer the following (Any Two)
10
Explain Nuclear Overhauser effect
Deduce the structure of the compound using following data
Molecular Formula: C8H7N
UV: 235 nm (ε 15000); IR: 2250, 1620, 1600, 1510
1H NMR in 2.4 15 7.2 J 8 Hz, 10 7.5 J 8 Hz, 10 mm).
Deduce the structure of the compound using following data
Molecular Formula: C8H8O2
UV: 250, 260, 265 nm (ε 220, 250, 220 respectively) IR: 3300-2700 1700, 1600 1500, 920
1H NMR in 3.5 12 7.2 30 12.3 6mm, exchange with D2O).
b)Answer the following (Any one)
04
Discuss chemically and magnetically equivalence phenomenon in NMR?
Explain Karlpus curve and discuss 3J coupling with examples?
Q.5
a)Answer the following (Any two)
14
Discuss FAB and MALDI techniques of mass spectroscopy?
Deduce the structure of organic compound using given spectral data.
Molecular Formula: C5H10O2 IR: 2972, 1741, 1437, 1362, 1248, 1148, 1098, 997, 880 cm-1
1H NMR in 0.95 J 6 Hz, 30 1.62 (sextet, J 6 Hz, 20 2.28 J 6 Hz, 20 3.65 30 mm). Mass: m/z 102 87, 74, 71, 59, 55, 43 42, 41, 59, 45 43; very weak.
Deduce the structure of organic compound using given spectral data.
Molecular Formula: C6H10O4
UV: 220 nm; IR in 1742, 3000; 1H NMR (200 MHz; CDCl3,
δ in 2.0 9 4.3 6 13C NMR (50 MHz; CDCl3, δ in 20, 62, 172. MASS: m/z 43 (base peak, 86, 146.