Organic Chemistry Some Basic Principles and Techniques Test

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Organic Chemistry Some Basic Principles and Techniques Test - 58

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Question 1
1 / -0

Consideration the addition of HBr to 3,3-Dimethyl-1-butene shown below. what is the best mechanism explanation for the formation of the observed product?

A
Protonation of the alkene followed by a hydride shift and addition of bromide to the carbocaton

B
Double bond shift in the alkene following by the protonation and addition of bromide to the carbocation

C
addition to bromide to the alkene followed by a double bond shift and protonation

D
Protonation of the alkene followed by a methyl shift and addition of bromide to the carbocation

Solution

This is an addition reaction which involves the formation of carbocation. First protonation of alkene takes place followed by methyl shift to stabilize carbocation. Then addition of bromine takes place.
Question 2
1 / -0

Product $$(C)$$ of above reaction is:

A
$$H_{2}C = CH_{2}$$

B
$$CH_{3} - C \equiv C - CH_{3}$$

C
$$HC \equiv CH$$

D
$$CH_{3} - CH = CH - CH_{3}$$

Solution

Hydrolysis of anhydrous gives carboxylic acids. On reacting with bases, the acidic hydrogen are lost. Kolbe's electrolysis results in evaporation of carbon dioxide from reactant.

Refer to image

Here acetylene is formed.
Question 3
1 / -0

Product (B) of the above reaction is:

A

B

C

D

Solution

As refer to the IMAGE $$01$$ dehydration reaction occur. So, double bond is formed and as refer to above IMAGE $$02$$ Acid catalysed carbocation rearrangement takes place here so $$6$$ membered ring is formed.
Question 4
1 / -0

What are reactant $$X$$ and product $$Y$$ in the following sequence of reactions ?

A

B

C

D

Solution

The reagent is not an inverting agent hence the configuration remains same in the first nucleophilic substitution reaction where -H is replaced.
Refer to image 01
The next reaction is also substitution where the configuration is inverses
Refer to image 02
Here, inversion of configuration takes place.
Question 5
1 / -0

Decreasing order of heat evolved upon catalytic hydrogenation of given reactants with $$H_2$$ (Pd/C) is:

A
b > c > a > d

B
d > a > c > b

C
d > c > a > b

D
a > b > c > d

Solution

As refer to the above image least stable – more heat of hydrogenation. So, Order of heat evolved is - $$d>a>a>b$$
Question 6
1 / -0

Arrange the following in increasing order of their acidic strength.

A
$$III < I < IV < II$$

B
$$II < I < IV < III$$

C
$$I < III < IV < II$$

D
$$II < III < I < IV$$

Solution

Acidic strength of a compound is increased due to presence of groups showing $$-I$$ effect. So, $$IV$$, having the strongest $$-I$$ effect, will be the most acidic, followed by $$I$$.
Between $$II$$ and $$III$$, $$III$$ will be more acidic as the removal of adjacent to $$-C=O$$ group is favored due to stronger $$-I$$effect by $$-C=O$$ group as well as ether group. The $$-I$$ effect is comparatively less in case of $$II$$.
Hence, the required order is: $$II<III<I<IV$$
Question 7
1 / -0

In the given selective hydrogenation which combination is incorrect?

A

B

C

D

Solution

In selective hydrogenation the less stable double bonds are hydrogenated first so the correct reaction is shown in the above image.
Question 8
1 / -0

$$2CH_3-\underset{Ph}{\underset{|}{C}}=CH_2 \to \xrightarrow{H-A(acid)}\underset{(major)}{(A)}$$
Product (A) is :

A

B

C

D
Question 9
1 / -0

Which of the following reaction do not present in the major product of the given Birch reductions

A
(i), (iii), (vi)

B
(iv), (vi), (vii)

C
(iv), (v), (vi)

D
(i), (ii), (v), (vii)

Solution

As refer to the IMAGE $$01$$, in Brich reduction, the benzene is converted to a diene and occurs through carbanion and free radical mechanism.

Since, it is an electron withdrawing group. Double bond is not attached with the group. $$Na$$ in liquid $$NH_3$$ is a reducing agent which converts triple bond into trans double bonds.

As refer to the IMAGE $$02$$ due to the conjugation, only one double bond is lost.
Question 10
1 / -0

The following reaction take place in high yields.
Use your knowledge of alkene chemistry to predict a product even through you have never seen this reaction before

A

B

C

D

Solution

Addition reaction occurs resulting in generation of carbocation which rearrange and forms rings and lastly dehydration occurs.