2 Chemistry -- Haloalkanes

When haloalkanes react with alc. sodium cyanide gives alkyl cyanide but when reacted with alc. silver cyanide gives alkyl isocyanide. Why? with example and reactions

1 Answers

CN ion is an ambidient nucleophile i.e. those ions which possess two possible sites to attack at the electron-deficient centre.

Both carbon and Nitrogen can supply a pair of electrons during the nucleophilic attack.

Alcoholic NaCN or KCN liberate CN^- ions freely as AgCN -----> Na⁺ + ^-CN (here C attacks first)

and form alkane nitriles as product.

However for alc. AgCN, the bond here is covalent bond. In this, C only has a polar negative charge which is less. Instead, N which has one lone pair acts as a nucleophile and attacks the haloalkane to form isocyanide.

How would you make chloretone from ethanol?

Again

Convert methyl chloride to acetyl chloride.

Why is halogenation of alkanes not a pure synthetic method for preparing alkyl halides?

1. Direct fluorination of alkanes is highly exothermic and explosive making it difficult to control.
2.Direct iodination of alkanes is highly reversible and difficult to carry out.

3. In direct chlorination and bromination, the reaction can lead to different isomeric monohalogenated alkanes (alkyl halides) as well as polyhalogenated alkanes.

Hence, halogenation of alkanes is not a good method of preparation of alkyl halides.

How would you distinguish ethanol propan-2-ol and 2-methylpropan-2-ol by victor Meyer's method?

How will you make (obtain) from chloroform:(a) Chloretone(b) Phenyl Isocynide(c) Acetylene(d) Salicaldehyde

(a) Chloretone is obtained from chloroform by the reaction of chloroform with acetone in the presence of base.

(b)Phenyl isocyanide isformed when chloroform is treated with alcoholic potassium hydroxide and aniline in carbylamine reaction.

(c)Chloroform and silver powder react with each other to form acetylene and silver salt.

(d)Salicylaldehyde is prepared byheating phenol and chloroform together in the presence of potassium hydroxide OR sodium hydroxide. This reaction is called the Reimer-...

Why haloalkanes reacts with aq. KOH to give alcohol but with alc. KOH gives alkene? With reactions

In an aqueous solution, KOH ionises completely to give OH^-ions. OH^-ion is a strong nucleophile, causing alkyl chloride to undergo a substitution reaction to form alcohol.

Whereas Alcoholic KOH is a strong base soit can abstract a hydrogen from the β-carbon of the alkyl chloride and form an alkene by eliminating a molecule of HCl.

Alkylhalides when reacted with alkoholic potassium nitrite gives alkyl nitrite but when reacted with alc. silver nitrite gives nitro alkane. Why with example and reaction

Nitrite ion is an ambident nucleophile because it has two sites — oxygen and nitrogen — through which attack can take place.Potassium nitrite (KNO₂) is predominantly ionic and one of the oxygen atoms has a negative charge (O=NOK⁺). Nucleophilic attack through this negatively charged oxygen atom mainly gives alkyl nitrite.

Silver nitrite (AgNO₂), on the other hand, is predominantly covalent and both oxygen and nitrogen atoms have lone pair of electrons. Since nitrogen is less electronegative...

Write structural isomers of C3H7Br and give thier IUPAC and common name and convert one isomer into another and viceversa.

The compound having the molecular formula $C3 H$ 7Brwill have two different structural isomers which are $1$ -bromopropane and $2$ -bromopropane.

Conversion:

Arrange each set of compounds in order of increasing boiling points.a. Bromomethane, Bromoform, Chloromethane, Dibromomethaneb. 1-Chloropropane, Isoproply chloride, 1-Chlorobutane

a. For the same alkyl group, boiling point increases with the increase in size of the halogen atom. Therefore, boiling point of bromomethane is more than that of chloromethane. Further, the boiling point increase in number of halogen atoms. Therefore, boiling point of bromoform is higher than that of dibromomethane, which is higher than that of bromomethane. Thus, the boiling point increases as:

Chloromethane < Bromomethane < Dibromomethane < Bromoform

b. For the same halogen, boiling...

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