Chemistry MCQs for NEET — Practice Questions with Answers

(d) In Lucas test when Lucas reagent is treated with 1$°$ ,2$°$  and 3$°$  alcohols, then turbidity appears, if turbidity is appeared immediately, then alcohol is tertiary. 2-methyl propan-2-ol is a tertiary alcohol. Hence, it reacts fastest with Lucas reagent.

The phenoxide ion (C₆H₅O^-) is stabilized by delocalization of the negative charge over the aromatic ring, making it more stable than the ethoxide ion (CH₃CH₂O^-). This increased stability results in a higher ionization constant for phenol.

(d) Alkanols are the derivates of alkanes which are derived by the replacement of -H of alkanes with -Oh (hydroxyl groups).

       C_nH_2n+2 →+OH-HC_nH_2n+1OH or C_nH_2n+2O

       Alkanes

weaker R.A

$$\begin{gathered} {\left({\mathrm{CH}}_3\right)}_3\mathrm{COH} \stackrel{{\mathrm{H}}_2{\mathrm{SO}}_4}{\to } ({\mathrm{CH}}_3{)}_2\mathrm{C}={\mathrm{CH}}_2 \\ \mathrm{Molar} \mathrm{mass} 74 \mathrm{Molar} \mathrm{mass} 56 \end{gathered}$$

      % yield =65

      Real yield = (56/74)x37x(65/100)=18.2 g

 This primary alcohols isomers of C₅H₁₁OH are 

(i)

${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2-\mathrm{OH}$

(ii)

${\mathrm{CH}}_3-\stackrel{{\mathrm{CH}}_3}{\stackrel{|}{\mathrm{CH}}}-{\mathrm{CH}}_2-{\mathrm{CH}}_2-\mathrm{OH}$

(iii)

${\mathrm{CH}}_3-{\mathrm{CH}}_2-\underset{{\mathrm{CH}}_3}{\underset{|}{\mathrm{CH}}}-{\mathrm{CH}}_2-\mathrm{OH}$

(iv)

 ${\mathrm{CH}}_3-\underset{{\mathrm{CH}}_3}{\overset{{\mathrm{CH}}_3}{\underset{\left|}{\overset{\right|}{\mathrm{C}}}}}-{\mathrm{CH}}_2-\mathrm{OH}$

Non-polar part C₆H₅- shows more hydrophobic nature.

Branching give rise to decrease in surface area and thus intermolecular forces are lowered.

(c) Molar mass of thioethers are more than ether.

Methanol (CH₃OH) does not contain a hydrogen atom attached to a carbon that is adjacent to an oxygen atom. Therefore, it does not undergo oxidation to form a yellow precipitate when heated with an alkaline solution of iodine.