Arrange basicity of given compounds in decreasing order.
(1) `OH`
(2) `CH_(3)-O`
(3) `CH_(3)-underset(CH_(3))underset(|)(CH)underset(CH_(3))underset(|)CHO`
(4) `CH_(3)-underset(CH_(3))underset(|)CH-O`

Options

A. 1, 2, 3, 4
B. 4, 3, 2, 1
C. 3, 4, 2, 1
D. 3, 4, 1, 2

Answer

To arrange the basicity of the given compounds in decreasing order, we need to analyze the stability of their conjugate acids and the effects of substituents on the basicity of the anions. Here’s a step-by-step solution:

### Step 1: Identify the Compounds
The compounds given are:
1. \( OH^- \) (Hydroxide ion)
2. \( CH_3O^- \) (Methoxide ion)
3. \( CH_3-CH(CH_3)-CH(CH_3)-O^- \) (Branched pentanol anion)
4. \( CH_3-CH(CH_3)-O^- \) (Secondary propanol anion)

### Step 2: Determine the Conjugate Acids
The basicity of these anions can be compared by looking at the acidity of their conjugate acids:
- The conjugate acid of \( OH^- \) is water \( H_2O \).
- The conjugate acid of \( CH_3O^- \) is methanol \( CH_3OH \).
- The conjugate acid of the branched pentanol anion is a branched pentanol (let's denote it as \( CH_3-CH(CH_3)-CH(CH_3)-OH \)).
- The conjugate acid of the secondary propanol anion is \( CH_3-CH(OH)-CH_3 \) (2-propanol).

### Step 3: Compare Acidity
Now we need to compare the acidity of these conjugate acids:
- Methanol \( CH_3OH \) is more acidic than water \( H_2O \).
- 2-Propanol is less acidic than methanol but more acidic than branched pentanol.
- Branched pentanol is less acidic than 2-propanol.

### Step 4: Order of Acidity
From the above analysis, we can summarize the order of acidity as follows:
1. Methanol \( (CH_3OH) \) - most acidic
2. Water \( (H_2O) \)
3. 2-Propanol \( (CH_3-CH(OH)-CH_3) \)
4. Branched Pentanol \( (CH_3-CH(CH_3)-CH(CH_3)-OH) \) - least acidic

### Step 5: Order of Basicity
The basicity of anions is inversely related to the acidity of their conjugate acids. Therefore, the order of basicity will be the opposite of the order of acidity:
1. Branched Pentanol Anion \( (CH_3-CH(CH_3)-CH(CH_3)-O^-) \) - most basic
2. 2-Propanol Anion \( (CH_3-CH(CH_3)-O^-) \)
3. Hydroxide Ion \( (OH^-) \)
4. Methoxide Ion \( (CH_3O^-) \) - least basic

### Final Order of Basicity
Thus, the final order of basicity in decreasing order is:
\[ \text{Branched Pentanol Anion} > \text{2-Propanol Anion} > \text{Hydroxide Ion} > \text{Methoxide Ion} \]

### Summary
The decreasing order of basicity is:
1. \( CH_3-CH(CH_3)-CH(CH_3)-O^- \) (Branched Pentanol Anion)
2. \( CH_3-CH(CH_3)-O^- \) (2-Propanol Anion)
3. \( OH^- \) (Hydroxide Ion)
4. \( CH_3O^- \) (Methoxide Ion)

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