Reaction Mechanisms - Organic Chemistry - Chemistry Previous Year Questions

1

2008 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2008

In the carbylamine reaction, R-X is converted to R-Y via the intermediate Z. R-X, R-Y and Z, respectively, are

A

R-NH₂, R-NC, carbene

B

R-NH₂, R-NC, nitrene

C

R-NC, R-NH₂, carbene

D

R-OH, R-NC, nitrene

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2

2008 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2008

Cyanogen bromide (CNBr) specifically hydrolyses the peptide bond formed by the C-side of

A

methionine

B

glycine

C

proline

D

serine

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3

2008 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2008

The major products P1 and P2, respectively, in the following reaction sequence are

A

Two five-membered rings with N-O and HN-O groups

B

One five-membered ring with N-O and one acyclic with OH

C

One five-membered ring with N-O and one ketone

D

One acyclic with NH-OH and one acyclic with NH2 and OH

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4

2008 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2008

o-Bromophenol is readily prepared from phenol using the following conditions

A

i) (CH3CO)2O; ii) Br2; iii) HCl-H2O, Δ

B

i) H2SO4, 100 °C; ii) Br2; iii) H3O+, 100 °C

C

N-Bromosuccinimide, dibenzoyl peroxide, CCl4, Δ

D

Br2/FeBr3

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5

2008 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2008

The photochemical reaction of 2-methylpropane with F2 gives 2-fluoro-2-methylpropane and 1-fluoro-2-methylpropane in 14:86 ratio. The corresponding ratio of the bromo products in the above reaction using Br2 is most likely to be

A

14 : 86

B

50 : 50

C

1 : 9

D

99 : 1

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6

2008 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2008

Compound X is

A

(CH₃O)₃P

B

(CH₃O)₂P(O)

C

(CH₃O)₂P(O)(OH)

D

(CH₃O)₃PH

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7

2009 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2009

The major product X (based on the preferred conformation) in the reaction
[Reaction Scheme: A cyclohexane derivative with OTs and OH groups trans-diaxial, treated with KH to give X]
is
(Ts = p-toluenesulfonyl)

A

[Structure: bicyclic ether with two fused cyclohexane rings]

B

[Structure: cyclohexene derivative with OTs group]

C

[Structure: unsaturated bicyclic ether]

D

[Structure: cyclohexene derivative with OH group]

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8

2009 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2009

Compounds Y and Z can be differentiated by carrying out basic hydrolysis, because

A

Y produces 4-methylphenol and Z is unaffected

B

Y produces 4-methylphenol and Z produces 4-methylbenzoic acid

C

Y is unaffected and Z produces 4-methylbenzoic acid

D

Y is unaffected and Z produces 4-methylphenol

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9

2011 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2011

In the reaction
\[\text{Optically pure (+)-trans-2-acetoxycyclohexyl tosylate} \xrightarrow{\text{HOAc, KOAc}\Delta} [\text{X}]\]
the major product [X] is

A

racemic trans-1,2-cyclohexanediol diacetate

B

optically active trans-1,2-cyclohexanediol diacetate

C

racemic cis-1,2-cyclohexanediol diacetate

D

optically active cis-1,2-cyclohexanediol diacetate

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10

2011 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2011

The compound [X] is

A

Me-CH(Br)-CH(Me)-CH=CH2 (SMILES: CC(Br)C(C)C=C)

B

Br-CH2-C(=O)-CH(Me)2 (SMILES: BrCC(=O)C(C)C)

C

Me-C(Br)(Me)-C(=O)-Me (SMILES: CC(C)(Br)C(C)=O)

D

Me-C(=O)-CH(Br)-Me (SMILES: CC(=O)C(Br)C)

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11

2012 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2012

Shown below is a Hammett plot obtained for the reaction
\[ \[\begin{array}{ccc}\] \[\ce{Ar-C(=O)Cl} & \xrightarrow{\ce{H2O}} & \ce{Ar-C(=O)OH}\] \end{array} \]
The change in slope of the plot indicates that

A

the reaction does not follow linear free energy relationship

B

electrons are being withdrawn from the transition state in the mechanism

C

electrons are being donated to the transition state in the mechanism

D

the mechanism of the reaction is changing

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12

2012 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2012

Identify the product from the following reaction
[Image of reaction]
(9-BBN = 9-Borabicyclo[3*3*1]nonane)

A

[Image of option A]

B

[Image of option B]

C

[Image of option C]

D

[Image of option D]

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13

2012 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2012

In the above reaction, X = Cl, Br or I. Based on the graph, identify the alkyl halides (R-X) as S1, S2 and S3

A

S1 = R-Cl, S2 = R-Br and S3 = R-I

B

S1 = R-I, S2 = R-Br and S3 = R-Cl

C

S1 = R-Cl, S2 = R-I and S3 = R-Br

D

S1 = R-I, S2 = R-Cl and S3 = R-Br

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14

2012 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2012

Identify product P₁ and its yield relative to P₂

A

P₁ is M and is the major product

B

P₁ is N and is the minor product

C

P₁ is N and is the major product

D

P₁ is M and is the minor product

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15

2013 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2013

The major product formed in the reaction of quinoline with potassium amide (KNH2) in liquid ammonia is

A

B

C

D

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16

2013 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2013

The major product formed in the Beckmann rearrangement of the compound given below is

A

B

C

D

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17

2014 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2014

The product of the following reaction gave 6 line ¹³C NMR spectrum with peaks at δ 175, 52, 50, 46, 37, 33 ppm. The structure of the product is

A

(image)

B

(image)

C

(image)

D

(image)

Check answer

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18

2016 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2016

The major product obtained in the following reaction, is

A

B

C

D

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19

2016 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2016

The major product obtained in the following reaction, is
Reaction: HC≡C-CH2OH, 1. LiNH2 (2 equiv.)/liq. NH3, 2. C2H5Br (1 equiv), 3. H3O⊕

A

CH3CH2-C≡C-CH2OH

B

H-C≡C-CH2OCH2CH3

C

CH3CH2-C≡C-CH2NH2

D

H-C≡C-CH2NH-CH2CH3

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20

2019 · Chemistry · Organic Chemistry · Reaction Mechanisms

Chemistry (CY) 2019

The product(s) formed in the following reaction is (are)

A

I only

B

II only

C

III only

D

mixture of I and II

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