ECAT Pre Engineering Chemistry Chapter 21 MCQ Test With Answer

Alkyl halides are reactive :

• High A
• Medium B
• Less C
• Least D

Tertiary alkyl halides are practically inert to substitution by S_N2 mechanism because of

• Onsolubility A
• Instability B
• Inductive effect C
• Steric hindrance D

Grignard reagent is not prepared in aqueous medium but prepared in ether medium because

• The reagent is highly reactive in ether A
• The reagent does not react with water B
• The reagent becomes inactive in water C
• The reagent reacts with water D

SN₂reactions can be best carried out with:

• Prl. alkyl halide A
• Sec. Alkyl halide B
• Ter. Alkyl halide C
• All of three D

Which halide among the following is used as methylating agent?

• CH₃l A
• C₂H₅Cl B
• C₂H₅Br C
• C₆H₅Cl D

Reation of which with Grignard's reagent gives primary alcohol:

• Formaldehyde A
• Aldehyde B
• Ketones C
• Acetone D

For which mechanisms, the first step involved is the same:

• E₁ and E₂ A
• E₂and SN₂ B
• E₂ and E₁ C
• E1 and SN₁ D

How many monochlorobutanes will be possible on chlorination of n-butane?

• 1 A
• 2 B
• 3 C
• 5 D

Which is a weak nucleophile

• OH^- A
• Br^- B
• NH₃ C
• CI^- D

Grignard's reagent on treatment with carbonyl compounds yield

• Pheonol A
• Alcohol B
• Alkane C
• None of these D

The rate of E₁reaction depends upon

• The concentration of substrate A
• The concentration of nucleophile B
• THe concentration of substrate as well as nucleophile C
• None of the above D

On warming with silver powder,chloroform is converted into

• Acetylene A
• Hexachloroethane B
• 1,1,2,2-tetrachloroethane C
• ethylene D

Each of the following compounds is effective as a refrigerant. The release of which one of these causes the greatest depletion of the ozone layer

• CCl₂F₂ A
• CH₃OCH₃ B
• CH₃CHF₂ C
• CH₃CH₂CH₃ D

Which of the following undergoes uncleophilic substitution exclusively by S_N1 mechanism?

• Benzyl chloride A
• Ethyl chloride B
• Chlorobenzene C
• Isopropyl choride D

The alkyl halide molecule on which a nucleophile attacks is called

• Substrate A
• Subsituent B
• Substituted C
• All of these D

Which of the following compounds could be prepared by reacting bromoethane with KCN and then reducing the product

• CH₃CH₃ A
• CH₃CH₂NH₂ B
• CH₃CH₂CH₂NH₂ C
• CH₃CH₂CH₃ D

• 2-bromo-3-methylbutane A
• 3-methyl-2-bromobutane B
• 2-methyl-3-bromobutane C
• All of these D

Organic compounds containing halogen atom are called:

• R---OH A
• R----X B
• R----NH₂ C
• R----COH D

An electrophile may be

• Positive A
• Negative B
• Neutral C
• Both c and a D

Alkyl halides react with Mg in dry ether to form

• Magnesium halide A
• Grignard's reagent B
• Alkene C
• Alkyne D

Alkyl halides on treatment with aqueous KOH give

• Phenol A
• Alcohol B
• Aldehyde C
• Ketone D

• Primary alkyl halide A
• Secondary alkyl halide B
• Tertiary alkyl halide C
• None of these D

Hydrolysis of Grignard's reagent gives:

• Alcohol A
• Halide B
• Alkyl C
• Alkane D

Best medhod of preparation of alkyl halide from alcohals is by its reaction with:

• HX A
• SOCl₂ B
• Px₅ and PX₃ C
• All D

The most reactive compound for electrophilic nitration will be

• Benzyl chloride A
• Benzoic acid B
• Nitrobenzene C
• Chlorobenzene D

Alkyl halides ae considered to be very reactive compounds towards nucleophiles because

• They have an electrophilic carbon A
• They have an electrophilic carbon and a good leaving group B
• They have an electrophilic carbon and a bad leaving group C
• They have a nucleophilic carbon and a good leaving group D

2-Bromopentane is heated with potassium ethoxide in ethanol . The major product obtained is

• 2-Ethoxypentane A
• Pent-1-ene B
• cis-Pent-2-ene C
• trans-Pent-2-ene D

E₁mechanism is generally shown by

• 1° - RX A
• 2° - RX B
• 3° - RX C
• None of these D

When primary amine reacts with chloroform in ethanolic KOH, then the product is

• An isocyanide A
• An aldehyde B
• A cyanide C
• An alcohol D

With the increase in size of halogen atom the reactivity of an alkyl halide

• Increases A
• Decreases B
• Remain constant C
• None of these D