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NEET Chemistry MCQ
Alcohols, Phenols And Ethers Mcq Neet Chemistry
Quiz 4
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Q.1
ion Q92) The major product formed in the following reaction [AIIMS 2005]
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a)
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b)
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c)
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d)
Explanation
The reaction is example of SN1 reaction Answer: (d)
Q.2
ion Q93) The major product obtained on the monobromination ( with Br2/FeBr3) of the following compound A is [ AIIMS 2006]
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a)
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b)
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c)
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d)
Explanation
The reaction is an example of electrophilic aromatic substitution. Although both OCH3 and CH3 groups are o,p- directing the OCH3 group dominates. Product (b) is favoured because the new group (Br) experience least hindrance Answer: (b)
Q.3
Which of the following compounds has the highest boiling point? [ AIIMS 2006]
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a) CH3CH2CH2Cl
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b) CH3CH2CH2CH2Cl
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c) CH3CH(CH3)CH2Cl
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d) (CH3)3CCl
Explanation
Molecules having higher molecular weight and less branching have higher boiling point Answer: (b)
Q.4
The major product formed in the following reaction CH3CH(Cl)CH2-CH2OH + aq.KOH → is : [ AIIMS 2006]
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a) CH3CH = CHCH2OH
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b) CH2 = CHCH2OH
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c)
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d) CH3CH(OH)CH2CH2OH
Explanation
Answer:(d)
Q.5
CH3OC2H5 and (CH3)3C-OCH3 are treated with Hydroiodic acid. The fragments obtained after reactions are [ AIIMS 2007]
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a) CH3I + HOC2H5 ; (CH3)3Cl+HOCH3
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b) CHO + C2C2H5I ; (CH3)3Cl+HOCH3
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c) CHO + C2C2H5I ; (CH3)3COH + CH3I
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d) CH3I + HOC2H5 ; CH3I + (CH3)3COH
Explanation
In case of unsymmetrical ethers, the site of cleavage depends on the nature of alkyl group CH3-O-C2H5 + HI → CH3I + C2H5OH [ At 373K] The alkyl halide is formed the smaller alkyl group. However, in case of tertiary alkyl ether following reaction occurs CH3-OC(CH3)3 + HI → (CH3)C-I + CH3OH The alkyl halide is formed from the tertiary alkyl group and the cleavage of such theirs occurs by SN2 mechanism as the product is controlled by the formation of more stable intermediate tertiary carbocation from protonated ether Answer: (a)
Q.6
In which of the following reactions the product obtained is t-butyl methyl ether? [ AIIMS 2008]
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a)
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b)
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c)
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d)
Explanation
It is Willamson's synthesis. It involves the nucleophilic attack of alkoxide ion on alkyl halide according to SN2 mechanism. In order to prepare methyl tertiary butyl ether , we must use methyl halide ( primary) and sodium ethoxide and t-alkyl halide because the latter undergoes elimination reaction rather than substitution Answer: (c)
Q.7
Which of the following is primary halide? [ AIIMS 2008]
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a) iso-propyl iodide
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b) secondary butyl iodide
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c) tertiary butyl bromide
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d) Neohexyl chloride
Explanation
Writing the structure Thus option(d) is primary halide Answer: (d)
Q.8
An organic compound X on treatment with pyridinium chlorochromate in dichloromethane gives compound Y. Compound Y reacts with I2 and alkali to form triiodomethane. The compound X is [ AIIMS 2008]
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a) C2H5OH
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b) CH3CHO
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c) CH3COCH3
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d) CH3COOH
Explanation
Compound Y must give iodoform test. Further since Y is obtained by the oxidation of X which must be an alcohol ( CH3CH2OH and thus Y is CH3CHO Answer:(a)
Q.9
Maximum enol content is in [AIIMS 2008]
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a)
0%
b)
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c)
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d)
Explanation
Maximum enol content is in structure (b) because here the enol form is stabilized by H-bonding Answer: (b)
Q.10
The formation of diethyl ether ethanol is based on [ AIIMS 2009]
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a) Dehydrogenation reaction
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b) Hydrogenation reaction
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c) Dehydration reaction
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d) Hetrolytic fission reaction
Explanation
Ethanol on dehydration forms diethyl ether Answer: (c)
Q.11
Chloropicrin is obtained by the reaction of [ AIIMS 2010]
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a) steam on carbon tetrachloride
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b) nitric acid on chlorobenzene
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c) chlorine on picric acid
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d) nitric acid on chloroform
Explanation
Chloropicrin is nitrochloroform. It is obtained by the nitration of chloroform with Nitric acid. Chloropicrin is liquid, poisonous and used as insecticide and in war gas HCCl3 + HNO3 → O2NCCl3 Answer: (d)
Q.12
on Q103) compound B is [ AIIMS 2011]
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a) (CH3)3CCOOH
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b) (CH3)3COH
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c) (CH3)3COC(CH3)3
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d) All the three
Explanation
CN- is a strong base and since the substrate is tert-halide, it mainly undergoes elimination reaction forming alkene(A). In presence of dil. H2SO4 alkenes undergo hydration in Markovnikov's way. Answer:(b)
Q.13
Ethanol can be prepared more easily by which reaction? [ AIIMS 2011] i) CH3CH2Br + H2O → CH3CH2OH ii) CH3CH2Br + Ag2O ( in boiling water) → CH3CH2OH
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a) by (i) reaction
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b) by (ii) reaction
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c) Both reactions proceed at same rate
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d) by none
Explanation
Heavy metal ions, particularly Ag+ catalyse SN1 reaction because of presence of empty orbital Answer: (b)
Q.14
THe formation of cyanohydrin from a ketone is an example of [ IIT 1998]
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a) Electrophilic addition
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b) Nucleophilic addition
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c) Nucleophilic substitution
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d) Electrophilic substitution
Explanation
Carbonyl compounds undergo nucleophilic addition Answer: (b)
Q.15
on Q106) IUPAC Name of the compound
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a) 3-N,N-dimethylamino-3-methylpentane
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b) 3-N,N-dimethylpentanammine
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c) 3-N,N-dimethyl-3-aminopentane
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d) 3,3-Dimethylamino-3-methylpentane
Explanation
Answer: (a)
Q.16
Among the following, the least stable resonance structure is [ IIT 2007]
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a)
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b)
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c)
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d)
Explanation
In (a), due to similar charges ( two positive charges) on adjacent atom, the structure is expected to be least stable Answer:(a)
Q.17
The correct stability order of the following resonance structure is [ IIT 2009] I) H2C = N + = N- II) H2C+ - N = N- III) H2C- - N+ ≡ N IV) H2C- = N+
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a) (I) > (II) > (IV) > (III)
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b) (I) > (III) > (II) > (IV)
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c) (II) > (I) > (III) > (IV)
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d) (III) > (I) > (IV) > (II)
Explanation
Stability of structure depends on (i) Number of π-bonds ∝ resonance energy ∝ stability (ii) Contributing structures should be such that negative charge resides on an electronegative element and positive on an electropositive element (iii) like charges should not reside on atoms closed to each other and unlike charges should not be widely separated. Thus order of stability in option (b) is correct Answer: (b)
Q.18
Grignard reagent is not prepared in aqueous medium but prepared in ether medium because
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a) The reagent is highly reactive in ether
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b) The reagent does not react with water
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c) The reagent becomes iactive in water
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d) The reagent reacts with water
Explanation
RmgX + H2O → RH + Mg(OH)X Answer: (d)
Q.19
SN1 reaction of alkyl halides leads to
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a) retention of configuration
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b) racemisation
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c) inversion of configuration
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d) none of these
Explanation
The incoming nucleophile can attack from any side of carbocation leading to formation of racemic mixture Answer: (b)
Q.20
A mixture of two organic compounds was treated with sodium metal in ether solution. iso-butane was obtained as a product. The two chlorine compounds are
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a) methyl chloride and propyl chloride
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b) methyl chloride and ethyl chloride
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c) isopropyl chloride and methyl chloride
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d) isopropyl chloride and ethyl chloride
Explanation
Answer:(c)
Q.21
Among the following, the molecule with highest dipole momentum is [ IIT 2003] Answer: (a)
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a) CH3Cl
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b) CH2Cl2
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c) CHCl3
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d) CCl4
Explanation
Answer: (a)
Q.22
Which of the following is the example of SN2 reaction?
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a) CH3Br + OH- → CH3OH + Br-
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b) CH3CH(Br)CH3 + OH - → CH3CH(OH)CH3 + Br-
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c) CH3CH2OH → CH2 = CH2
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d) (CH3)2C(Br)CH3 + OH- → (CH3)2C(OH)CH3 + Br-
Explanation
Methyl halides are most reactive towards SN2 reactions. Order of reactivity towards SN2 reaction is CH3-X > 1o > 2o > 3o > Answer: (a)
Q.23
The molecular formula of saturated compound is C2H4Br2 the formula permit the existence of two ...
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a) functional isomers
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b) position isomers
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c) optical isomers
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d) cis - trans isomers
Explanation
Two position isomers are possible Answer: (b)
Q.24
A compound which does not give iodoform test on treatment with alkali and iodine is [ Roorkee 1993]
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a) Ethanol
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b) Acetone
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c) Diethyl ketone
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d) Isopropyl alcohol
Explanation
Only diethyl ketone CH3CH2COCH2CH3 does not contain the group CH3CO- or CH3OH and hence does not give iodoform test Answer:(c)
Q.25
Benzene reacts with n-propyl chloride in the presence of anhydrous AlCl3 to give [ CBSE-PMT 1993]
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a) 3-propyl-1-chlorobenzene
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b) n-propylbenzene
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c) no reaction
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d) isopropylbenzene
Explanation
Answer: (d)
Q.26
When wine is kept in air, it becomes sour due to .... ... [ Chandigarh CET 1998]
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a) Bacteria
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b) Oxidation of C2H5OH into CH3COOH
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c) Virus
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d) Formic acid
Explanation
In air ethanol gets oxidised to acetic acid Answer : (b)
Q.27
In glycerine .... ....
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a) One primary -OH group is present
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b) One tertiary -OH group is present
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c) Two secondary -OH groups are present
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d) One secondary -OH group is present
Explanation
Glycerine contains three -OH groups out of which two are primary and one is secondary Answer : (d)
Q.28
Absolute ethyl alcohol can be converted to diethyl ether by heating it to 410K in the presence of .... ... [ Bihar CEE 1992]
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a) Dil. H2SO4
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b) Dil. HCl
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c) Conce. H2SO4
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d) Conc. CH3COOH
Explanation
In presence of Conce. H2SO4 reaction Produce Diethyl ether 2C2H5OH → C2-O-C2H5 + H2O Answer : (c)
Q.29
Scientific study of fermentation was first made by ,,, ,,, [ MP CET 1994]
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a) Buchner
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b) Liebig
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c) Biot
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d) Pasture
Explanation
Answer : (d)
Q.30
An organic compound A reacts with methyl magnesium iodide to form an addition product which on hydrolysis forms the coumpound B, Compound B gives blue colour salt in Victor Meyer's test. The compounds A and B respectively are .... ... [ Tamil Nadu CET 2002]
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a) Acetaldehyde, t-butyl alcohol
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b) Acetaldehyde, ethyl alcohol
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c) Acetaldehyde, iso-propyl alcohol
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d) Acetone, iso-propyl alcohol
Explanation
In Victor Meyer's test, blue colour salt is given by secondary alcohol. It means compound B must be a secondary alcohol Only aldehydes with Grignard reagent yield secondary alcohols. Aldehyde should have one carbon less than secondary alcohol since Grignard reagent contain methyl group. These conditions are satisfied by acetaldehyde and iso-propyl alcohol Answer : (c)
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