Organic Chemistry Multiple Choice Questions on “Nuclear Magnetic Resonance – 1”.
1. Which of the following organic compound with molecular formula C3H C12 exhibits only one signal in the IH NMR spectrum?
a) 2, 2-dichloropropane
b) 1, 2-dichloropropane
c) 1, 3-dichloropropane
d) 1, 1-dichloropropane
Answer: a
Clarification: Only (a) compound has all chemically equivalent hydrogen. So, give only one peak.
2. The 1H NMR spectrum of CH3OCHCICH2Cl will exhibit ________
a) A three proton doublet. One proton singlet and a two proton doublet
b) A three proton singlet. One proton singlet and a two proton doublet
c) A three proton singlet. One proton triplet and a two proton doublet
d) A three proton triplet. One proton triplet and a two proton triplet
Answer: c
Clarification: The 1H NMR spectrum of CH3OCHCICH2Cl will exhibit three proton singlet, one proton triplet and two proton doublet.
No. of peaks = n + 1
(n = no. of neighbouring chemically equivalent Hydrogen nuclii)
3. Which of the following 1H-NMR spectrum of compound with molecular formula C4H9NO2 shows delta 5.30 (broad, IH), 4.10(q, 2H), 2.80 (d, 3H), 1.20 (t, 3H) ppm?
a) CH3NHCOOCH2CH3
b) CH3CH2NHCOOCH3
c) CH3OCH2CONHCH3
d) CH3CH2OCH2CONH2
Answer: a
Clarification: C4H9NO2;
chemical shift = 5.30 (broad, 1H)
chemical shift = 4.10 (q, 2H)
chemical shift = 2.80 (d, 3H)
chemical shift = 1.20 (t, 3H)
As shown in the above compound, doublet, because of neighbouring 1H attached to N and one will be broad as because of hydrogen attached to N, quatret becauseof neighbouring 3H and finally triplet, because
of neighbouring 2H.
4. Which of the following has three types of hydrogens in the following compounds?
a) Br-CH = CH2
b) CH3 – CH2 – CH3
c) C6H5CH2
d) CH3– CH2 – CH(CH3) – N02
250+ TOP MCQs on Alkanes and Answers
Answer: a
Clarification:
We will replace them by D and check the structure if they are different then they are different.
both are different
so, total 3 type of hydrogen
So, three different type of hydrogen is present in compound a.
5. Which of the compound show only one signal is present in the PMR spectra?
a) C3H4, C3H6
b) C4H6, C5H12
c) C8H18, C2H6O
d) All of the mentioned
Answer: d
Clarification: All of the below compounds have only type of proton, so only one signal.
6. How many Hertz does 1 ppm correspond to for an PMR spectrometer operating at a radio frequency of 60 MHz and 100 MHz?
a) 6 Hz, 10 Hz
b) 60 Hz, 100 Hz
c) 100 Hz, 60 Hz
d) 10Hz, 100Hz
Answer: b
Clarification:
7. Compound C4H10O gave PMR spectrum consisting of two groups of lines (multiplets) with relative intensities in the ratio 3 : 2. Other compound of the same formula exhibited two lines with relative area of 9 : 1. What are these compounds.
a) Diethyl ether and n-butanol
b) t-Butyl alcohol and 1-Methoxypropane
c) diethyl ether and t-Butyl alcohol
d) Diethyl ether and 2-Methoxypropane
Answer: c
Clarification: NMR data: Two groups of lines in 3 : 2 and two groups of lines in 9 : 1 for same molecular formula
a) CH3–CH2–O–CH2–CH3
6Ha -> 1 group of line;
4Hb -> 1 group of line
Therefore, Intensity => 6 : 4 => 3 : 2.
b) 
9H -> 1 group of line and 1H -> 1 group of line / single peak.
Therefore, Intensity => 9 : 1.
