NEET Chemistry Questions: Basic Principles of Orgainc Chemistry

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A strong base can abstract an α-hydrogen from





Key Idea: The carbon which is more electrophilic in nature, loses an α-H with a base more readily. Among the given compounds, carbonyl carbon (>C=O) ie, ketone is more electrophilic in nature, thus loses an α

 

 

Which of the following represents the correct order of the acidity in the given compounds ?





(d) The acidity of halogenated acid increases almost proportionately with the increase in electronegativity of the halogen present.

So, the correct order is:

FCH2COOH > CICH2COOH > BrCH2COOH > CH3 COOH

If there is no rotation of plane polarized light by a compound in a specific solvent, thought to be chiral, it may mean that:





(d) An optically active compound rotate plane polarized light. But due to some external compensation (heat, light, catalyst, solvent etc), the optically active compound lose their optical activity. The compound then exists as racemic mixture i.e, both d and l form are present in solution due to some intramolecular rearrangement.

So, there is no rotation of plane polarised light and compound does not have an asymmetric centre and when it again forms the symmetric centre both d- and l forms are obtained in equal amount.

For the following :

(i) I-

(ii) Cl-

(iii) Br-

the increasing order of nucleophilicity would be :





Halogens are the most reactive elements. High reactivity is due to their low dissociation energy. Further among halogens reactivity decreases as we move down the group. 

In case of different nucleophiles, but present in the same group in the periodic table, then larger is the atomic mass, higher is the nucleophilicity. Hence the decreasing order of nucleophilicity of the halide ions is I- > Br- > Cl- > F- 

The Lassaigne's extract is boiled with conc. HNO3  while testing for the halogens. By doing so it :-





When the Lassaigne's extract is boiled with concentrated HNO3, it decomposes Na2S and NaCN (if formed during the test) to prevent their interference in the detection of halogens. This step ensures that the precipitation of AgCl is due to the presence of halogens in the given organic compound.

Ether and benzene can be separated by :-





Ether Boiling point = 34.5° C

Benzene boiling point = 80°C 

Both can be separated by Distillation.

In the Kjeldahl's method for estimation of nitrogen present in a soil sample, ammonia evolved from 0.75 g of sample neutralized 10 mL of 1 M H2SO4. The percentage of nitrogen in the soil is:





10 ml of  corresponds to 10 mmol.


It will neutralize 20 mmol of  . 

Weight of .

Thus 0.75 g of sample of organic compound contains 0.280 g of nitrogen. 
 
The percentage of nitrogen in the organic sample is %.