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 Among the following compounds, the increasing order of their basic strength is
Option: 1  (I) < (II) < (IV) < (III)
Option: 2  (I) < (II) < (III) < (IV)
Option: 3  (II) < (I) < (IV) < (III)
Option: 4  (II) < (I) < (III) < (IV)
 

Among the following compounds, the increasing order of their basic strength is (II)<(I)<(IV)<(III)
(III) is most basic due to +I effect of −CH3 group attached to N. This increases electron density on N so that N can easily donate its lone pair of electrons to suitable acid.
(II) is least basic as the lone pair of electrons on N is part of pi electrons of aromatic ring. Donation of this lone pair of electrons will break the stability of the aromatic ring.
(I) is less basic than (IV) as the lone pair of electrons on N is in conjugation with aromatic ring.

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Posted by

vishal kumar

The increasing order of the boiling points for the following compounds is :
Option: 1  (III) < (IV) < (II) < (I)
Option: 2 (IV) < (III) < (I) < (II)
Option: 3  (II) < (III) < (IV) < (I)
Option: 4 (III) < (II) < (I) < (IV)  
 

The increasing order of boiling point is

\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OCH}_{3}<\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{CH}_{3}<\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}<\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}

in C2?H5?OH (i) C-O bond is polar & form hydrogen bonding in H2?O

 in C2?H5?Cl → C-Cl bond is polar but less than that of C-O bond
so boiling point of C2?H5?Cl is less than that of C2?H5?OH
in C2?H5?OCH3?   , the C-O bond is polar but the weak polarity of ethers do not appreciably affect their boiling points

And alkane has the least boiling point than above compounds.

Answer: (1)

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vishal kumar

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In the following structure, the double bonds are marked as I, II, III and IV Geometrical isomerism is not possible at site (s) :
Option: 1  III
Option: 2  I
Option: 3  I and II
Option: 4  III and IV  
 

Geometrical isomerism is not possible at Site I as two identical methyl groups are attached to the same carbon bearing the double bond.

Hence, the answer is Option (2)

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vishal kumar

A compound of molecular formula C8H8O2 reacts with acetophenone to form a single cross-aldol product in the presence of base.  The same compound on reaction with conc. NaOH forms benzyl alcohol as one of the products.  The structure of the compound is :  
Option: 1

Option: 2 

Option: 3 

Option: 4 
 

The structure of the compound is : 

Correct option 1

 

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vishal kumar

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A flask contains a mixture of isohexane and 3-methylpentane. One of the liquids boils at \mathrm{63 \degree C} while the other boils at \mathrm{60 \degree C}. What is the best way to separate the two liquids and which one will be distilled out first?
Option: 1 Fractional distillation, isohexane
Option: 2 simple distillation,3-methylpentane
Option: 3 fractional distillation, 3 - methylpentane
Option: 4 simple distillation, isohexane
 

As we have learnt,

 

Distillation and fractional distillation -

Simple distillation is a procedure by which two liquids with different boiling points can be separated. Simple distillation can be used effectively to separate liquids that have some major degrees difference in their boiling points. As the liquid being distilled is heated, the vapours that form will be richest in the component of the mixture that boils at the lowest temperature. Purified compounds will boil, and thus turn into vapours, over a relatively small temperature range (2 or 3°C) by carefully watching the temperature in the distillation flask, it is possible to affect a reasonably good separation.

As distillation progresses, the concentration of the lowest boiling component will steadily decrease. Eventually, the temperature within the apparatus will begin to change; a pure compound is no longer being distilled.

Steps to be followed in simple distillation process:    

(i) Take a mixture(Acetone and water) in the distillation flask fit it with the thermometer.
(ii) Arrange the apparatus as shown in the given figure.
(iii) Heat the mixture slowly keeping a close watch on thermometer.
(iv) Since the acetone has lower boiling point starts vaporises and condenses in the condenser which is finally collected in the beaker.

 

 Note: Simple distillation is effective only when separating a volatile liquid from a nonvolatile substance. If the liquids comprising the mixture that is being distilled have boiling points that are closer than 50 degrees to one another, the distillate collected will be richer in the more volatile compound but not to the degree necessary for complete separation of the individual compounds.

 

Fractional distillation is used for the mixture of two liquids which differ in their boiling point by 10-15 K. It is a type of distillation which involves the separation of miscible liquids. The process involves repeated distillations and condensations and the mixture is usually separated into component parts. In this method a fractionating column is used to increase the cooling surface area so that ascending vapour phase become richer in more volatile component and descending liquid phasebecome richer in less volatile component.

The basic principle of this type of distillation is that different liquids boil and evaporate at different temperatures. So when the mixture is heated, the substance with lower boiling point starts to boil first and convert into vapours.

Fractinal distillation is used for seperation of 

(i) Acetone (b.pt. 329 K) from methyl alcohol (b.pt. 338 K)

(ii) Crude oil into various useful fractions such as gasoline, kerosene oil, lubricating oil, etc.

Steps to be followed in fractional distillation process:

1. After setting up the apparatus, a mixture of two miscible liquids A and B is taken where A has more volatility than substance B.

2. The solution is added into the distilling flask while the fractionating column is connected at the tip of the flask. Heat is applied which increases the temperature slowly. The mixture then starts to boil and vapours start rising in the flask.

3. The vapours are from the volatile component A. The vapours then start moving through the fractionating column into the condenser where it is cooled down to form a liquid which is collected in the receiver.

Throughout the process, vaporization and condensation take place repeatedly until the two mixtures are separated completely.

 

-

Liquid having lower boiling point comes out first in fractional distillation. Simple distillation can't be used as boiling point difference is very small.

Therefore, Option(1) is correct.

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vishal kumar

The one that will show optical activity is : (en=ethane-1,2-diamine)
Option: 1

Option: 2

Option: 3 


Option: 4     

As we have learnt,

Optically active species do not contain any plane of symmetry or centre of symmetry.

Therefore, option (3) is correct.

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Posted by

Ritika Jonwal

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The number of water molecule(s) not coordinated to copper ion directly in  CuSO_{4}\cdot 5H_{2}O is :
Option: 1 2
Option: 2 3
Option: 3 1
Option: 4 4

CuSO_{4}\cdot 5H_{2}O contains four water molecules directly co-ordinated to Cu^{2+} and the one water molecule is connected to the Complex with the help of H-bonding as shown in the diagram given below

Therefore,option (3) is correct.

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Posted by

Ritika Jonwal

The major product obtained in the following reaction is:
Option: 1
Option: 2
Option: 3
Option: 4
 

As we have learnt, 

The first step of the reaction is the Carbylamine reaction which produces an isocyanide from primary amine. Second step is the reduction process in which both the cyanide as well as the isocyanide is converted into their respective amines.

The reaction occurs as 

Hence, the correct answer is Option (4)

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Ritika Jonwal

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Which of the following compounds will show the maximum 'enol' content?
Option: 1 CH_{3}COCH_{2}COOC_{2}H_{5}
Option: 2 CH_{3}COCH_{2}COCH_{3}
Option: 3 CH_{3}COCH_{3}
Option: 4 CH_{3}COCH_{2}CONH_{2}
 

Difinition of Tautomerism -

Tautomers are isomers of a compound that differ only in the position of the protons and electrons. The carbon skeleton of the compound is unchanged. A reaction that involves simple proton transfer in an intramolecular fashion is called tautomerism.

The stability of enol depends on the factors

(1) Resonance

(2) Hydrogen-bonding

(3) Hyperconjugation

(4) Hydrogen which is removed from \alpha- carbon should be acidic in Nature for enol formation.

CH2 is present between 2- electron-withdrawing group,  It is having acid 'H'

                        

Over the resonance effect decreases because of cross conjugation. So the stability of the enol form decreases.

The two -dicarbonyl compounds have a higher enol content than the two mono carbonyl compounds because hydrogen bonding and conjugation stabilize their enols. The enol content in C (a mono aldehyde) is higher than D because of the reasons outlined above. 

Therefore, option (2) is correct.

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Ritika Jonwal

The number of chiral carbons in chloramphenicol is ________
 

 

The structure of chloramphenicol is given below:

 

Thus, the number of chiral carbons in chloramphenicol is 2.

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Posted by

Kuldeep Maurya

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