Tag: chemistry

Questions Related to chemistry

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

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

  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. $C _{2}H _{5}OH and CH _{3}OCH _{3}$

Show answer
Correct Option: B
Explanation:

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

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

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

  1. $LiAlH _{4}$

  2. $BH _{3}$ in $THF$

  3. $PCl _{3}$

  4. $K _{2}Cr _{2}O _{7}/H^{+}$

Show answer
Correct Option: A,B
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 $LiAlH _4$.

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:

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

  1. $CH _3COOH$

  2. $CH _3CHO$

  3. $CH _3CH _2I$

  4. $CH _3CH _3$

Show answer
Correct Option: D
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.

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

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

  1. $LiAIH _{4}$

  2. $N/alcohol$

  3. $Zn/HCl$

  4. $H _{2}/Ni$

Show answer
Correct Option: A
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.

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

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

  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. $CH _3-CH(OH)-CH _2-COOH$

Show answer
Correct Option: C

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

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

  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} $

Show answer
Correct Option: A
Explanation:

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

What happens when a carboxylic acid is treated with lithium aluminium hydride?

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

  1. Aldehyde is formed.

  2. Primary alcohol is formed.

  3. Ketone is formed.

  4. Grignard reagent is formed.

Show answer
Correct Option: B
Explanation:

$RCOOH + 4H \xrightarrow{LiAlH _4}RCH _2OH+H _2O$

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 :

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

  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. $W \, is\, CH _3-(CH _2) _{16}-CHO$

Show answer
Correct Option: A,B,C
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$

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

reactions of haloarenes haloalkanes and haloarenes chemistry

  1. $CH _3I> CH _3Br> CH _3Cl$

  2. $CH _3Cl> CH _3Br> CH _3I$

  3. $CH _3Br> CH _3Cl> CH _3I$

  4. $CH _3Br> CH _3I> CH _3Cl$

Show answer
Correct Option: A
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. 

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

reactions of haloarenes haloalkanes and haloarenes chemistry

  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

Show answer
Correct Option: B
Explanation:

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