Aldehydes Ketones and Carboxylic Acids Test

Result

Aldehydes Ketones and Carboxylic Acids Test - 22

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Question 1
1 / -0

Ethanol on reaction of acidified potassium dichromate form:

A
ethane

B
ethene

C
ethanal

D
ethanoic acid

Solution

$$C_2H_5OH + K_2Cr_2O_7/ {H}^{+} \rightarrow CH_3CHO \rightarrow CH_3COOH$$

Ethanol is first oxidised to ethanal and then to ethanoic acid.
Potassium dichromate is a very strong oxidising agent, ethanol on oxidation, the dichromate ion (IV) solution which is orange in colour is reduced to a green colour Cr(III) ion solution. This reaction is used in detecting the presence of alcohol in breath in suspected drunken drivers.

Hence, the correct option is D.
Question 2
1 / -0

Chlorinaton of toluene in the presence of light and heat followed by treatment with aqueous NaOH gives

A
o-cresol

B
p-cresol

C
salt

D
benzoic acid

Solution
Question 3
1 / -0

Out of the following the one that undergoes reaction with 50% NaOH solution to give corresponding alcohol and acid is:

A
phenol

B
benzaldehyde

C
butanol

D
benzoic acid

Solution

The reaction of benzaldehyde to form alcohol and acid can be written as:
$$C_{6}H_{5}CHO \xrightarrow[H_{3}O^{-}]{NaOH} C_{6}H_{5}COOH + C_{6}H_{5}CH_{2}OH$$
The reaction is also called as Cannizzaro's reaction. This reaction can be given by only those aldehyde which does not contain alpha carbon.
Question 4
1 / -0

Identify the compounds which give yellow precipitate with $${I}_{2}+NaOH$$
(a) Ethyl alcohol (b) Acetone
(c) Propyl alcohol (d) 2-propanol
(e) 3- butanone (f) Butanal

A
c, e and f

B
a, d and f

C
e, f and a

D
a, b and d

Solution

The reaction of iodine and base with methyl ketones gives the appearance of a yellow precipitate, is used to probe the presence of a methyl ketone. This is also the case when testing for secondary alcohols (methyl alcohols. Ethyl alcohol, Acetone and 2-propanol gives positive test.
Question 5
1 / -0

In the sequence of reaction
$$C_2H_2\xrightarrow[HgSO_4]{H_2SO_4}A\overset{[O]}{\longrightarrow}B$$ The compound B is:

A
ethanoic acid

B
propanone

C
ethanol

D
methanal

Solution

In this reaction, first hydrolysis of ethyne takes place to form acetaldehyde which on further oxidation forms acetic acid as a product.
Question 6
1 / -0

You can make an organic acid from ethanol and that is:

A
$$\displaystyle { C }_{ 3 }{ H }_{ 7 }OH$$

B
found in bees and ants

C
acetic acid

D
formic acid

E
butanoic acid

Solution

You can make an organic acid from ethanol and that is acetic acid.
The fermentation of dilute (15%) ethyl alcohol with a living organism Mycoderma aceti in presence of air gives vinegar. Vinegar is a dilute solution of acetic acid (7-8%). Vinegar is then neutralized with lime to form calcium acetate which is then distilled with conc. sulphuric acid to form pure acetic acid.
Question 7
1 / -0

The $$\displaystyle p{ K }_{ a }$$ values of four carboxylic acids are given below. Identify the weakest carboxylic acid.

A
4.89

B
1.28

C
4.76

D
2.56

Solution

The weakest carboxylic acid has highest value of pKa and lowest value of Ka. The weakest carboxylic acid is the carboxylic acid with pKa 4.89.
Question 8
1 / -0

A tripeptide is written as glycine-alanine-glycine. The correct structure of the tripeptide is:

A

B

C

D

Solution
Question 9
1 / -0

Structure of ethanoic acid is:

A
$$\displaystyle { CH }_{ 3 }-{ CH }_{ 2 }-{ CH }_{ 3 }$$

B
$$\displaystyle CH_3-\underset {\displaystyle \underset {\displaystyle O}{ ||}}{C}-OH$$

C
$$\displaystyle { CH }_{ 3 }-O-{ C }_{ 3 }{ H }_{ 7 }$$

D
$$\displaystyle CH_3-\underset {\displaystyle \underset {\displaystyle O}{ ||}}{C}-CH_3$$

E
$$\displaystyle CH_3 - CH_2- NH_2$$

Solution

Structure of ethanoic acid is $$\displaystyle CH_3-\underset {\displaystyle \underset {\displaystyle O}{ ||}}{C}-OH$$. It is also called acetic acid. It can be considered as compound formed by substituting the hydrogen atom of methane with carboxylic group $$-COOH$$.
Question 10
1 / -0

Ethyl ethanoate on reacting with excess of $${CH}_{3}MgBr$$ will give

A
acetone

B
2-methyl-2-propanol

C
isobutanol

D
n-butyl alcohol

Solution

Ethyl ehtanoate on reacting with excess of $${CH}_{3}MgBr$$ gives 2-methyl-2-propanol.