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Multiple choice chemistry alcohols, esters and carboxylic acids reduction of carboxylic acids chemical properties chemical properties of carboxylic acids

$CH _{3}COOH \xrightarrow[]{LiAlH _{4}}(A)\xrightarrow[H _{2}]{Ni} B$ In this reaction A and B respectively are :

  1. $CH _{3}OH and CH _{4}$
  2. $C _{2}H _{5}OH and C _{2}H _{6}$
  3. $CH _{3}CHO and C _{2}H _{5} OC _{2}H _{5}$
  4. $C _{2}H _{5}OH and CH _{3}OCH _{3}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

B
$LiAlH _{4}$ reduces ethanoic acid to ethanol and then $H _{2}$ / Ni reduces it further to alkane.

Multiple choice chemistry alcohols, esters and carboxylic acids reduction of carboxylic acids chemical properties chemical properties of carboxylic acids

The reagent(s) used for converting ethanoic acid to ethanol is/are :

  1. $LiAlH _{4}$
  2. $BH _{3}$ in $THF$
  3. $PCl _{3}$
  4. $K _{2}Cr _{2}O _{7}/H^{+}$
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

$BH _3$ in $THF$ being a strong reducing agent, can efficiently convert carboxylic acid into the corresponding primary alcohol. Also, $LiAlH _4$ being a strong reducing agent, releases $H^-$ ions in enough quantity to convert carboxylic acid to the corresponding alcohol. So, ethanoic acid can be converted to ethanol using $BH _3$ in $THF$ and $LiAlH _4$.

Multiple choice chemistry alcohols, esters and carboxylic acids reduction of carboxylic acids chemical properties chemical properties of carboxylic acids

Methyl alcohol when reacted with carbon monoxide using cobalt or rhodium as catalyst , compound $'A'$ is formed. $'A'$ on heating with HI in the presence of red phosphorus as catalyst $'B'$ is formed. $'B'$ is:

  1. $CH _3COOH$
  2. $CH _3CHO$
  3. $CH _3CH _2I$
  4. $CH _3CH _3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$CH _3OH+CO\xrightarrow [ (High\quad Pressure) ]{ CO/Rh } \underbrace{ CH _3COOH} _{Compound A}$

Alcohol with carbon monoxide in presence of  $CO/Rh$ gives carboxylic Acid.
$CH _3COOH\quad \underrightarrow{Red P+HI}\quad CH _3-CH _3$
$Red P+HI$  is areducing agent and reduces carboxylic acid into hydrocarbons.

Multiple choice chemistry alcohols, esters and carboxylic acids reduction of carboxylic acids chemical properties chemical properties of carboxylic acids

Alcohols can be obtained from carboxylic acids by reduction using one of the following reagents:

  1. $LiAIH _{4}$
  2. $N/alcohol$
  3. $Zn/HCl$
  4. $H _{2}/Ni$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$RCOOH  +  LiAlH _4 \rightarrow RCHO  \rightarrow RCH _2OH $

Carboxylic acids along with lithium aluminium hydride, initially gives aldehyde and then reduced to primary alcohols.

Multiple choice chemistry alcohols, esters and carboxylic acids reduction of carboxylic acids chemical properties chemical properties of carboxylic acids

Which optically active compound on reduction with $\displaystyle LiAlH _{4}$ will give optically inactive compound?

  1. $CH _3-CH(OCH _3)-COOH$
  2. $CH _3-CH _2-CH(OH)-COOH$
  3. $CH _3-CH _2-CH(CH _2OH)-COOH$
  4. $CH _3-CH(OH)-CH _2-COOH$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Reduction of CH3-CH2-CH(CH2OH)-COOH with LiAlH4 yields CH3-CH2-CH(CH2OH)-CH2OH. This molecule has a chiral center at the carbon attached to the ethyl group, but the two CH2OH groups are not identical in a way that would make it achiral. Wait, actually, the reduction of the carboxylic acid to a primary alcohol creates a molecule where the two groups attached to the chiral center might become identical. Let's re-evaluate: CH3-CH2-CH(CH2OH)-COOH reduces to CH3-CH2-CH(CH2OH)-CH2OH. The chiral carbon is attached to H, ethyl, CH2OH, and CH2OH. Since two groups (CH2OH) are identical, it becomes achiral.

Multiple choice chemistry alcohols, esters and carboxylic acids reduction of carboxylic acids chemical properties chemical properties of carboxylic acids

The organic product formed in the reaction. $C _{6}H _{5}COOH \xrightarrow[(II)H _{3}O]{(I)LiAIH _{4}}$?

  1. $C _{6}H _{5}CH _{2}OH$
  2. $C _{6}H _{5}OHCH _{4}$
  3. $C _{6}H _{5}CH _{3} and CH _{3} OH$
  4. $C _{6}H _{5}CH _{3} and CH _{4} $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

using LAH (lithium aluminium hydride), the COOH group is reduced to  $ CH _{2} OH$  group

Multiple choice chemistry alcohols, esters and carboxylic acids reduction of carboxylic acids chemical properties chemical properties of carboxylic acids

Consider the following reaction $CH _3-(CH _2) _{14}-COOH \overset{LiAlH _4}{\longrightarrow} \,X \overset{HCl}{\longrightarrow}$
Palmitic acid
$ Y \overset{1.\, Mg/Et _2O}{\underset{2.\, Oxirane}{\longrightarrow}} Z \overset{KMnO _4}{\longrightarrow} W$
The correct identity of the compounds is/are :

  1. $X \,is \,CH _3-(CH _2) _{14}-CH _2OH$
  2. $Y\, is \, CH _3-(CH _2) _{14}-CH _2Cl$
  3. $Z \,is\, CH _3-(CH _2) _{16}-CH _2OH$
  4. $W \, is\, CH _3-(CH _2) _{16}-CHO$
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

Reaction:
$CH _3-(CH _2) _{14}-COOH \overset{LiAlH _4}{\longrightarrow} \,CH _3-(CH _2) _{14}-CH _2OH \overset{HCl}{\longrightarrow} CH _3-(CH _2) _{14}-CH _2Cl$
$ CH _3-(CH _2) _{14}-CH _2Cl \overset{1.\, Mg/Et _2O}{\underset{2.\, Oxirane}{\longrightarrow}} CH _3-(CH _2) _{16}-CH _2OH \overset{KMnO _4}{\longrightarrow} CH _3-(CH _2) _{16}-COOH$

Multiple choice reactions of haloarenes haloalkanes and haloarenes chemistry

The order of reactivities of methyl halides in the formation of Grignard reagent is :

  1. $CH _3I> CH _3Br> CH _3Cl$
  2. $CH _3Cl> CH _3Br> CH _3I$
  3. $CH _3Br> CH _3Cl> CH _3I$
  4. $CH _3Br> CH _3I> CH _3Cl$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Grignard reagents are highly reactive and react with any source of a proton to give hydrocarbons. Water, alcohol, amines are sufficiently acidic to convert them to corresponding hydrocarbons. Halide reactivity increases in the order $Cl < Br < I$

Therefore A is the correct option. 

Multiple choice reactions of haloarenes haloalkanes and haloarenes chemistry

Grignard reagent, a very useful starting compound for a number of organic reaction can be prepared by:

  1. reaction of alkyl halides with a solution of magnesium hydroxide

  2. reaction of alkyl halide with dry magnesium powder in presence of dry ether
  3. reaction of $MgCl _2$ with ether and alcohol

  4. rection of alkyl halide with magnesium in presence of alcohol
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$R-X+Mg\xrightarrow{dryether} R-Mg-X$
                                        grignard reagent