Question

(٣٩) من المخطط التالي:

A $\xrightarrow{تحلل~مالي~قاعدي}$ B $\xrightarrow{أكسدة~تامة}$ C

الصيغة العامة للمركب (C) هي $C_nH_{2n}O$

أي مما يلي يعبر عن المركبات (C ، B ، A)؟

• A. A: كلورو إيثان ، B: إيثانول ، C: أسيت الدهيد.
• B. A: 1- برومو بيوتان ، B: بيوتانول ، C: حمض بيوتانويك.
• C. A: كلوريد أيزوبروبيل ، B: 2- بروبانول ، C: بروبانال.
• D. A: 2- كلورو بروبان ، B: 2- بروبانول ، C: بروبانون.

Answer 1

Answer: (D)

A: 2- كلورو بروبان ، B: 2- بروبانول ، C: بروبانون.

Answer 2

The problem describes a two-step reaction sequence starting from compound A, going through B, and ending with C. We are given the general formula for compound C as $C_nH_{2n}O$. We need to identify the correct set of compounds (A, B, C) that fits this scheme.

Let's analyze the reaction steps:

1. A $\xrightarrow{\text{تحلل مائي قاعدي}}$ B: This step represents the basic hydrolysis of compound A to form compound B. This reaction is characteristic of alkyl halides (A) reacting with a base to form alcohols (B). $R-X + OH^- \rightarrow R-OH + X^-$ So, A is an alkyl halide and B is an alcohol.

2. B $\xrightarrow{\text{أكسدة تامة}}$ C: This step represents the complete oxidation of alcohol B to form compound C. The general formula for compound C is given as $C_nH_{2n}O$. This general formula corresponds to either an aldehyde (RCHO) or a ketone ($R_2CO$).

Now let's consider the oxidation of different types of alcohols:

• Primary alcohols (RCH₂OH):
  • Partial oxidation yields an aldehyde (RCHO), which has the general formula $C_nH_{2n}O$.
  • Complete oxidation yields a carboxylic acid (RCOOH), which has the general formula $C_nH_{2n}O_2$.
• Secondary alcohols (R₂CHOH):
  • Oxidation (often referred to as complete oxidation in this context as ketones are generally resistant to further oxidation without C-C bond cleavage) yields a ketone ($R_2CO$), which has the general formula $C_nH_{2n}O$.
• Tertiary alcohols (R₃COH):
  • Tertiary alcohols are generally resistant to oxidation without breaking carbon-carbon bonds.

Given that the product C has the general formula $C_nH_{2n}O$, C must be either an aldehyde or a ketone.

If B were a primary alcohol, its "complete oxidation" would typically lead to a carboxylic acid ($C_nH_{2n}O_2$), which contradicts the given formula $C_nH_{2n}O$.

Therefore, B must be a secondary alcohol, as its oxidation product (ketone) perfectly matches the general formula $C_nH_{2n}O$.

If B is a secondary alcohol, then A must be a secondary alkyl halide.

Option 4 is correct because it involves a secondary alkyl halide (A) converting to a secondary alcohol (B), which then oxidizes to a ketone (C). This perfectly matches all conditions, including the general formula for C.