NEET Questions Solved


Aldehydes and ketones will not form crystalline derivatives with                            

(a) sodium bisulphite

(b) phenyl hydrazine

(c) semicarbazide hydrochloride

(d) dihydrogen sodium phosphate

(d) Dihydrogen sodium phosphate (NaH2PO4) does not react with aldehydes and ketones because NaH2PO4 does not have any lone pair of electron on phosphorus atom, so it cannot act as a nucleophile.

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Acetone reacts with iodine (I2) to form iodoform in the presence of

(a) CaCO3          (b) NaOH          (c) KOH            (d) MgCO3

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Which of the following compounds with molecular formula, C5H10 yields acetone on ozonolysis? 

(a) 2-methyl-2-butene

(b) 3-methyl-1-butene

(c) Cyclopentane

(d) 2-methyl-1-butene

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Among acetic acid, phenol and n-hexanol which one of the following compound will react with NaHCO3 solution to give sodium salt and CO2?                                             

(a) Acetic acid

(b) n-hexanol

(c) Acetic acid and phenol

(d) Phenol

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The reagent used for the separation of acetaldehyde from acetophenone is

(1) NaHSO3         (2) C6H5NHNH2            (3) NH2OH              (4) NaOH and I2

 

(1) NaHSO3 gives the addition reaction with aldehyde and only aliphatic ketone. Acetophenone is the aromatic ketone so it does not give the addition product with NaHSO3 aldehyde from the addition product with NaHSO3 which on treatment with acid or base give again aldehyde.

 

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Iodoform test is not given by

(a) 2-pentanone                  (b) ethanol

(c) ethanal                          (d) 3-pentanone

(d) The compounds which contain either CH3-CO-group or  group give positive iodoform test. In 2-pentanone, (CH3CH2CH2COCH3)CH3CHO and C2H5OH, these groups are present, thus they give iodoform as follows

CH3-COCH2-CH2CH3 +3I2 +4NaOHCHI3+ CH3CH2CH2COONa +3NaI +3H2O

                                                            Iodoform(yellow ppt.)

CH3CHO +3I2 +4NaOHCHI3 +HCOONa +3NaI +3H2O

                                     Iodoform(yellow ppt.)

C2H5OHI2CH3CHO

CH3CHO +3I2 +4NaOHCHI3 +HCOONa +3NaI +3H2O#

                                      Iodoform

but due to absence of  or  group in 3-pentanone, it does not give iodoform.

 +I2 +NaOHNo reaction.

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Products of the following reaction                                   

  CH3CC.CH2CH3 (ii) hydrolysis(i) O3 ... are

(a) CH3CHO + CH3CH2CHO

(b) CH3COOH + CH3COCH3

(c) CH3COOH + HOOC.CH2CH3

(d) CH3COOH + CO2

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Which alkene on ozonolysis gives CH3CH2CHO and CH3COCH3?                                          

(a) CH3CH2CH=C<CH3CH3

(b) CH3CH2CH=CHCH2CH3

(c) CH3CH2CH=CHCH3

(d) CH3-C|=CHCH3           CH3

(a) When O3 reacts with alkene, it forms ozonide, which on reaction with Zn and acid or H2/Ni gives aldehydes and/or ketones. These products helps in locating the position  of  a double bond as

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Which one of the following on oxidation gives a ketone?                       

(a) primary alcohol                     (b) secondary alcohol

(c) tertiary alcohol                      (d) All of these

(b) Ketones can be prepared by the oxidation of secondary alcohols by using oxidising agent such as K2Cr2O7/H2SO4.

     >H3CH3CCHOH + [O]   >H3CH3CC=O + H2O

        2° alcohol               Dimethyl ketone

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Consider the following transformations

CH3COOH CaCO3AheatBNaOHI2C The molecular formula of C is                       

 

Due to haloform reaction, i.e. indicate the presence of a ethyl ketone product iodoform is yellow and has a characteristics odor. presence of 

It gives haloform reaction.

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