### Core Logic For a compound to release mathrmCO_2$\mathrm{CO}_2$ upon reaction with aqueous mathrmNaHCO_3$\mathrm{NaHCO}_3$, its acidity must be strictly greater than that of carbonic acid (mathrmH_2CO_3$\mathrm{H_2CO_3}$). Let's evaluate the acidity of the options: 1. **Picric Acid** (2,4,6-trinitrophenol - Option A): Extremely acidic (pK_a approx 0.38$pK_a \approx 0.38$) due to three strong electron-withdrawing nitro groups. Reacts with mathrmNaHCO_3$\mathrm{NaHCO}_3$ easily. 2. **4-Nitrobenzoic Acid** (Option B): Carboxylic acids generally have pK_a approx 4text--5$pK_a \approx 4\text{--}5$. More acidic than carbonic acid (pK_a approx 6.3$pK_a \approx 6.3$). Reacts with mathrmNaHCO_3$\mathrm{NaHCO}_3$. 3. **Anilinium Chloride** (Option 3): A salt of a strong acid and weak base. The anilinium ion is quite acidic (pK_a approx 4.6$pK_a \approx 4.6$) and easily decomposes mathrmNaHCO_3$\mathrm{NaHCO}_3$. 4. **4-Nitrophenol** (Option D): Only one nitro group is present. Its acidity (pK_a approx 7.15$pK_a \approx 7.15$) is weaker than carbonic acid. Hence, it does not react with sodium bicarbonate to yield effervescence of mathrmCO_2$\mathrm{CO}_2$. ### Pattern Recognition Acid-bicarbonate test shortcut: - All carboxylic acids and picric acid give a positive bicarbonate test. - Normal phenols and mono/di-nitrophenols are too weak to decompose bicarbonate. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Chemistry: Alcohols, Phenols and Ethers Class 12 Chemistry: Carboxylic Acids

### Core Logic Statement I: Dimethyl ether (CH_3OCH_3$CH_3OCH_3$) is highly soluble in water because its smaller alkyl chain allows substantial hydrogen bonding with water molecules. In contrast, diethyl ether has a larger hydrophobic ethyl group which drastically reduces its water solubility (to about 7.5text g$7.5\text{ g}$ per 100text mL$100\text{ mL}$). Thus, Statement I is true. Statement II: Sodium metal (Na$Na$) reacts violently with alcohols like ethyl alcohol to release hydrogen gas: 2textC_2textH_5textOH + 2textNa rightarrow 2textC_2textH_5textONa + textH_2uparrow$2\text{C}_2\text{H}_5\text{OH} + 2\text{Na} \rightarrow 2\text{C}_2\text{H}_5\text{ONa} + \text{H}_2\uparrow$ Since diethyl ether has no active acidic hydrogen, it does not react with sodium metal. Hence, sodium can dry diethyl ether but cannot be used for ethyl alcohol. Statement II is true. ### Pattern Recognition Ethers are miscible with water primarily when the non-polar alkyl parts are very small. Active hydrogen presence (-textOH$-\text{OH}$ group in alcohols) prevents the use of alkali metals like sodium for moisture removal. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Chemistry: Alcohols, Phenols and Ethers

### Core Logic Williamson Ether Synthesis operates strictly via an **S_N2$S_N2$ mechanism**. To optimize ether formation yields, the alkyl halide component MUST be primary (1^circ$1^\circ$) or methyl to evade spatial shielding restrictions. Let us review the alkyl halide across the options: * Option 1: Ethyl bromide (textEtBr$\text{EtBr}$) is 1^circ$1^\circ$ rightarrow$\rightarrow$ Excellent ether yield via substitution. * Option 2: Methyl bromide (textCH_3textBr$\text{CH}_3\text{Br}$) is a unhindered methyl halide rightarrow$\rightarrow$ High substitution efficiency. * Option 3: n-Propyl bromide (textn-PrBr$\text{n-PrBr}$) is 1^circ$1^\circ$ rightarrow$\rightarrow$ Clean substitution pathway. * Option 4: sec-Butyl bromide (textsec-BuBr$\text{sec-BuBr}$) is a secondary (2^circ$2^\circ$) alkyl halide. When a sterically hindered 2^circ$2^\circ$ halide is treated with a strongly basic alkoxide reagent like isobutoxide, **alkene elimination (E2$E2$) competes aggressively and dominates** as the major pathway over nucleophilic substitution (S_N2$S_N2$).

### Pattern Recognition Williamson Synthesis Rule: Alkoxide can be as massive and complex as desired (3^circ$3^\circ$ or branched), but the Alkyl Halide MUST be unhindered (1^circ$1^\circ$ or methyl). If the halide is 2^circ$2^\circ$ or 3^circ$3^\circ$, elimination wins, forming an alkene instead of an ether. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Chemistry: Alcohols, Phenols and Ethers

### Core Logic Anisole (Ph-O-CH_3$Ph-O-CH_3$) contains an aryl-oxygen bond which possesses partial double bond character due to resonance stabilization with the aromatic ring. When treated with HBr$HBr$, protonation yields an oxonium ion. The nucleophile Br^-$Br^{-}$ attacks via an S_N2$S_N2$ pathway at the smaller, less hindered methyl group, cleaving the O-CH_3$O-CH_3$ bond to form Phenol (PhOH$PhOH$) and CH_3Br$CH_3Br$.

### Pattern Recognition Aromatic sp^2$sp^2$ C-O$C-O$ bonds are exceptionally strong and cannot be cleaved by nucleophilic attack from Hal^-$Hal^{-}$. Therefore, the oxygen always stays attached to the benzene ring, yielding phenol. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Chemistry: Alcohols, Phenols and Ethers