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Sunday, February 2, 2020

Which of the Complex of the following pairs has the largest value of CFSE? (1) [Co(CN)6]3- and [Co(NH3)6]3+ (2) [Co(NH3)6]3+ and [CoF6]3- (3) [Co(H2O)6]3+ and [Rh(H2O)6]3+ (4) [Co(H2O)6]2+ and [Co(H2O)6]3+

(1)  CN is the stronger ligand than NH3 therefore CFSE of [Co(CN)6]3-  will be more than  [Co(NH3)6]3+

(2) NH3 is stronger ligand than F therefore CFSE of [Co(NH3)6]3+ will be more than [CoF6]3-.
(3) Co belongs to 3d series whereas The Rh belong to 4d series. More the value of n more is CFSE therefore CFSE of  [Rh(H2O)6]3+  is more than [Co(H2O)6]3+ .
(4) Oxidation number of Co  in [Co(H2O)6]3+ is more than the Oxidation number of [Co(H2O)6]2+  therefore, CFSE of [Co(H2O)6]3+ is more than  [Co(H2O)6]2+.

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Saturday, February 1, 2020

What is oil of vitriol ?


Concentrated sulphuric acid is a dense and  oily liquid which is also known as oil of vitriol.  Concentrated sulphuric acid has a specific gravity of 1.84 and a boiling point of 611 K. The high boiling point and high viscosity indicate that sulphuric acid has associated structure due to hydrogen bonding as shown below:
The concentrated acid is soluble in water and the dissolution process is highly exothermic. So acid is always diluted by adding acid to the water slowly and not by adding water to acid. This is done because in the later case, lot of heat is produced which causes the acid to spurt out of the container.
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What are the groups that LiAlH4 can and cannot reduce?

Lithium aluminium hydride (LiAIH4) is a nucleophilic reducing agent, and used to reduce polar multiple bonds like >C=O, -CN bond because it is hydride (H-) donor. And it is simply abbreviated as LAH.
LIAIH4 can reduce:
(1) Aldehydes to primary alcohols,
(2) Ketones to secondary alcohols,
(3) Carboxylic acids and esters to primary alcohols.
(4) Acid chlorides to primary alcohols.
(5) Ester to primary alcohols.
(6) Acid anhydrides to primary alcohols.
(7) Amides and nitriles to primary amines.
(8) Isonitriles to secondary amines.
(9) Epoxides (Cyclic ethers) to alcohols.
(10) lactones (Cyclic esters) to diols. 

Important Notes:
LiAH4 can reduce Aldehydes, ketones, carboxylic acids, ester, acid chlorides, acids anhydrides, acid amides,  Nitro Compounds and nitriles and isonitriles  without attacking (Isolated non polar bonds , like -C=C- ) double bonds present in the Compounds. The only exception in this case alpha- Beta unsaturated compounds containing phenyl group in the Beta position, in this case LiAH4 also attack on double bond.
We can say that the double or triple bonds in conjugation with the polar multiple bonds can be reduced.



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Oxymercuration demercuration hydration procedure is superior to acid- catalysed hydration of most alkenes. Why ?

Oxymercuration demercuration hydration procedure is superior to acid- catalysed hydration of most alkenes. Because (1) the two stage process of oxymercuration demercuration is fast and takes place under mild condilions and gives more than 90 % yield of alcohol and (2) rearrangement doesn't take place hence most desire product easily obtained.
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Arrange the following groups in order of their increasing tendency for nucleophilic addition reactions -COO-, -COOH, -COOCH3, -COCH3, -CHO, -COCI, -CONH2. Justify your answer.


The tendency, for nucleophilic additions of a carbonyl group is increased with increasing partial positive charge on the carbonyl carbon atom, which is maximum in -COCl and minimum in -COO-. Thus, the required order is:



      "-COCI > -CHO > -COCH3 > -COOCH3 > -CONH2 > -COOH > -COO-"
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