Multiple Choice Questions
Q.1 The hybridizatio of central carbon in transition state is?
A) sp
B) sp2
C) sp3
D) dsp2
Q.2 The SN1 reactions are
A) zero order
B) 1st order
C) 2nd order
D) 3rd Order
Q.3 The rate of SN1 reaction depends upon
A) Ionization
B) Conc.of RX
C) Slow step
D) All of above
Q.4 The retention in structural configuration of RX in SN2 reactions is
A) 100%
B) 50%
C) 75%
D) 0%
Q.5 which one of the following is common in SN1 & E1
A) Rate of reaction
B) Order of reaction
C) 1st step of ionization
D) Type of reaction
Q.6 The characteristic reactions of alkyl halides are
A) Electrophilic substitution
B) Nucleophilic substitution
C) Beta elimination
D) Addition
Q.7 Ethyl bromide + Excess NH3 ------> ?
*? in that above reaction is
A) Ethyl amine
B) Diethyl amine
C) Triethyl amine
D) Tetraethylammine
Q.8 The CH3-CH2-X is converted into ___________ on reaction with alcoholic KOH
A) Ethanol
B) Ethene
C) Ethanoic acid
D) Ethane
Q.9 The all are primary alkyl halides except
A) n-Propyl chloride
B) Neo-pentyl chloride
C) iso-bytyl chloride
D) iso-propyl chloride
Q.10 The complete products of following reaction are
CH3CH2OH + PBr3 -----> Products
A) CH3CH2Br + H3PO3
B) CH3CH2Br + POBr3 + HCl
C) CH3CH2Br + H3PO4
D) CH3CH2Br + H2O
Q.11 The best reducing agent can be used for complete reduction of Alkanoic acids is
A) NaBH4
B) LiAlH4
C) HI/P
D) H2/Ni
Q.11 The best reducing agent can be used for complete reduction of Alkanoic acids is
A) NaBH4
B) LiAlH4
C) HI/P
D) H2/Ni
Answers:
1) B
2) B
3) D
4) D
5) C
6) B
7) A
8) B
9) D
10) A
11) C
EXPLANATION:
Q.1
When Alkyl halides reacts with nucleophile a transition state is formed in which carbon is plannar according to three hydrgen atoms with sp2 hybridization because in transition state the carbon is attached with three hydrogen atoms with single bond to each atom and one bond with halogen atom in the process of breaking and one bond with nucleophile in the process of formation so thses two bonds does not count to determine hybridization.Only complete bonds are considered to determine hybridization of central carbon atom in transition state.
Q.2
The SN1 reaction is nucleophilic unimolecular reaction. It is two step process in which 1st step is slow and rate determining step.The order of reaction always depends upon rate determining step so SN1 reactions are 1st order because only alkyl halide is involved in rate determining step and rate depends upon only concentration of it.
Rate = [Alkyl Halide]1
Q.3
As explained above in Q.2 rate of SN1 reaction depends upon slow step,concentration of alkyl halide and ionization of tertiary alkyl halide.
Q.4
The 100% inversion takes place in SN2 reactions so 0% retention takes place in SN2 reactions.
Q.5
In both SN1 and E1 the first step is same i.e; ionization of tertiary alkyl halide molecule however in both reactions the second step is different i.e; nucleophilic substitution in SN1 and beta elimination in E1 reaction.
Q.6
The characteristics reactions of alkyl halid family are nucleophilic substitution reactions (SN)
Q.7
If Ethyl bromide reacts with excess of ammonia it will produce primary ammine but if excess concentration of ethyl bromide reacts with ammonia it will produce quatanary ammine.If both are one mole each than primary alkyl halide will produce.
Q.8
The Ethyl halide is converted into alkenes by reacting with alc.KOH (Alcoholic KOH) but it will converted into alcohol if reacts with Aq.KOH(Aqueous KOH).
Q.9
Iso-propyl chloride is secondary alkyl halide.
Q.10
Ehyl bromide and phosphorous acid (H3PO3) are products when ethyl bromide reacts with PBr3.
Q.11
HI/P (Hydrogen iodide in the presence of red phosphorous) is strong reducing agent is used to convert carboxylic acids(alkanoic acids) into alkanes on complete reduction. But with LiAlH4 carboxylic acids are only partially reduced into alcohols.
11) C
EXPLANATION:
Q.1
When Alkyl halides reacts with nucleophile a transition state is formed in which carbon is plannar according to three hydrgen atoms with sp2 hybridization because in transition state the carbon is attached with three hydrogen atoms with single bond to each atom and one bond with halogen atom in the process of breaking and one bond with nucleophile in the process of formation so thses two bonds does not count to determine hybridization.Only complete bonds are considered to determine hybridization of central carbon atom in transition state.
Q.2
The SN1 reaction is nucleophilic unimolecular reaction. It is two step process in which 1st step is slow and rate determining step.The order of reaction always depends upon rate determining step so SN1 reactions are 1st order because only alkyl halide is involved in rate determining step and rate depends upon only concentration of it.
Rate = [Alkyl Halide]1
Q.3
As explained above in Q.2 rate of SN1 reaction depends upon slow step,concentration of alkyl halide and ionization of tertiary alkyl halide.
Q.4
The 100% inversion takes place in SN2 reactions so 0% retention takes place in SN2 reactions.
Q.5
In both SN1 and E1 the first step is same i.e; ionization of tertiary alkyl halide molecule however in both reactions the second step is different i.e; nucleophilic substitution in SN1 and beta elimination in E1 reaction.
Q.6
The characteristics reactions of alkyl halid family are nucleophilic substitution reactions (SN)
Q.7
If Ethyl bromide reacts with excess of ammonia it will produce primary ammine but if excess concentration of ethyl bromide reacts with ammonia it will produce quatanary ammine.If both are one mole each than primary alkyl halide will produce.
Q.8
The Ethyl halide is converted into alkenes by reacting with alc.KOH (Alcoholic KOH) but it will converted into alcohol if reacts with Aq.KOH(Aqueous KOH).
Q.9
Iso-propyl chloride is secondary alkyl halide.
Q.10
Ehyl bromide and phosphorous acid (H3PO3) are products when ethyl bromide reacts with PBr3.
Q.11
HI/P (Hydrogen iodide in the presence of red phosphorous) is strong reducing agent is used to convert carboxylic acids(alkanoic acids) into alkanes on complete reduction. But with LiAlH4 carboxylic acids are only partially reduced into alcohols.
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