Organic Spectroscopy (UV-Vis Spectroscopy) MCQs for CSIR NET, GATE - ChemContent

Chapter: Organic Spectroscopy
Topic: (UV-Visible) Spectroscopy 
Content: MCQ Questions & Solutions
Source: CSIR NET, GATE etc. Exams

Quiz                    PDF

Q1 The absorption at λ_max 279 nm (ε=15) in the UV spectrum of acetone is due to

[NET June 2011]

         (a) π → π* transition

         (b) n → π* transition

         (c) σ → σ* transition

         (d) π → σ* transition

Q2 In the UV-Vis spectrum, a diterpenoid exhibit a λ_max at 275 nm. The compound among the choices given below is

[NET June 2013]

Q3 In the UV-Vis spectrum of an α,β-unsaturated carbonyl compound, with increasing solvent polarity,

[NET June 2016]

         (a) n-π* transitions undergo hypsochromic shift, π-π* undergo bathochromic shift

         (b) n-π* transitions undergo bathochromic shift, π-π* undergo hypsochromic shift

         (c) both n-π* and π-π* transitions undergo bathochromic shift

         (d) both n-π* and π-π* transitions undergo hypsochromic shift

Q4 On the basis of Woodward-Fieser rules designs that have λ_max values in the range 268-273 nm are

[GATE 2003]

         (a) P and Q

         (b) P and R

         (c) Q and R

         (d) Q and S

Q5 Which of the following absorptions are shown by 1,3-butadiene in its UV absorption spectrum recorded in n-hexane (ε_max is the molar absorptivity)?

[GATE 2006]

         (a) λ_max 217 nm (ε_max = 21000)

         (b) λ_max 214 nm (ε_max = 210)

         (c) λ_max 253 nm (ε_max = 50000)

         (d) λ_max 250 nm (ε_max = 500)

Q6 Match the observed principle absorption in the visible spectrum shown in List-I with the bond shows this absorption in List-II

[GATE 2007]

List-I                List-II

(1) σ-σ*             (i) C-C

(2) n-σ*             (ii) C-O

(3) n-π*             (iii) C=O

(4) π-π*             (iv) C=C

         (a) 1-(i) ,2-(ii) ,3-(iii) ,4-(iv)

         (b) 1-(i) ,2-(iii) ,3-(ii) ,4-(iv)

         (c) 1-(ii) ,2-(i) ,3-(iv) ,4-(iii)

         (d) 1-(iv) ,2-(ii) ,3-(iii) ,4-(i)

Q7 Given the fact that 1,3-butadiene has a UV absorption of 217 nm, the absorption wavelength (in nm) for the conjugated system shown below is ____

[GATE 2014]

(use these absorption values for auxochromic groups: alkyl- +5, exo-cyclic double bond- +5, every additional conjugated C=C- +30)

Ans Key:

1.b  2.c  3.a  4.d  5.a  6.a  7.[282] 

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