Amines - Class 12

Consider the following aromatic amines in an aqueous solution at $298\text{ K}$:

I. Benzenamine II. 2-Methylbenzenamine III. $N,N$-Dimethylbenzenamine IV. $N,N,2$-Trimethylbenzenamine

Which of the following represents the correct decreasing order of their basic strength ($K_b$)?

Consider the exhaustive ammonolysis of methyl iodide (\ce{CH3I}) and ethyl iodide (\ce{C2H5I}) in separate reaction vessels, followed by the isolation of the respective primary ($1^\circ$), secondary ($2^\circ$), and tertiary ($3^\circ$) amines.

Let $A_{max}$ and $A_{min}$ be the most basic and least basic amines (among the $1^\circ, 2^\circ$, and $3^\circ$ amines) derived from \ce{CH3I} in aqueous solution at 298 K. Let $B_{max}$ and $B_{min}$ be the most basic and least basic amines (among the $1^\circ, 2^\circ$, and $3^\circ$ amines) derived from \ce{C2H5I} in aqueous solution at 298 K.

Calculate the value of $(x + y)$, where $x$ is the total number of $\alpha$-hydrogens in $A_{max}$ and $A_{min}$, and $y$ is the total number of $\alpha$-hydrogens in $B_{max}$ and $B_{min}$.

(Note: $\alpha$-hydrogens are the hydrogen atoms attached to the carbon atoms directly bonded to the nitrogen atom).

Consider an aqueous buffer solution containing equimolar amounts of the purine base Guanine and the amino acid L-Arginine, maintained at $\text{pH} = 7.4$ and $298\text{ K}$. Guanine contains multiple nitrogen atoms (labeled N1, N2, N3, N7, N9 by standard IUPAC purine numbering) and exhibits lactam-lactim tautomerism. The side chain of Arginine features a guanidino group containing both $sp^2$ and $sp^3$ hybridized nitrogen atoms. Which of the following statements correctly identifies the thermodynamic protonation states, the most basic sites, and the underlying electronic effects governing these molecules under the specified conditions?

Consider the following substituted anilines: (I) \ce{p-Fluoroaniline} (II) \ce{p-Chloroaniline} (III) \ce{2,4,6-Trinitroaniline} (IV) \ce{N,N-Dimethyl-2,4,6-trinitroaniline}

Which of the following represents the correct decreasing order of their basic strength in aqueous medium at $298\text{ K}$?

Aniline undergoes electrophilic aromatic substitution with a nitrating mixture (conc. \ce{HNO3} and conc. \ce{H2SO4}) at $288\text{ K}$ to form three mononitrated products $P$, $Q$, and $R$ with yields of $51\%$, $47\%$, and $2\%$ respectively. Product $Q$ is isolated and treated with \ce{NaNO2}/\ce{HCl} at $273-278\text{ K}$, followed by reaction with \ce{H3PO2} and \ce{H2O} to yield compound $X$. In a parallel experiment, aniline is first treated with acetic anhydride in the presence of pyridine, then nitrated using the same nitrating mixture at $288\text{ K}$, and finally hydrolyzed with dilute \ce{H2SO4} to give compound $S$ as the major product. $S$ is then subjected to diazotization (\ce{NaNO2}/\ce{HCl} at $273-278\text{ K}$) followed by a Sandmeyer reaction with \ce{CuCN}/\ce{KCN} and subsequent complete acidic hydrolysis to yield compound $Y$. Identify compounds $X$ and $Y$.

Aniline is treated with $\ce{NaNO2 / HCl}$ at $273\text{ K}$ to yield compound $\textbf{P}$. Compound $\textbf{P}$ is then reacted with $m$-aminophenol under two distinct conditions:\n(i) In an aqueous buffer at $\text{pH} = 9.5$ to yield $\textbf{X}$ as the major product.\n(ii) In an aqueous buffer at $\text{pH} = 4.5$ to yield $\textbf{Y}$ as the major product.\nIdentify the correct IUPAC names for $\textbf{X}$ and $\textbf{Y}$.

An equimolar mixture of 4-methylaniline and (S)-2-amino-3-phenylpropanoic acid is treated with one equivalent of benzenesulfonyl chloride ($\ce{PhSO2Cl}$) in an aqueous buffer solution at $\text{pH} = 7.0$ and $298\text{ K}$. Which of the following represents the major organic product(s) isolated from this reaction?

Consider the basicity of Cytosine (4-amino-1H-pyrimidin-2-one) and Aniline in aqueous solution at 298 K. Upon treatment with one equivalent of dilute \ce{HCl_{(aq)}}, both molecules form thermodynamically stable monoprotonated cations. Identify the major site of protonation for Cytosine and Aniline, respectively, and the correct comparative basicity of their exocyclic \ce{-NH2} groups.

Consider the following reaction sequences for nitrobenzene ($\ce{C6H5NO2}$):

Sequence I: $\ce{C6H5NO2} \xrightarrow{\ce{LiAlH4,\ dry\ ether}} \ce{P}$

Sequence II: $\ce{C6H5NO2} \xrightarrow{\ce{Sn/HCl}} \xrightarrow{\ce{NaOH(aq)}} \ce{Q} \xrightarrow{\ce{NaNO2,\ HCl,\ 273\ K}} \ce{R} \xrightarrow[\ce{pH \approx 9-10}]{\ce{Phenol}} \ce{S}$

Identify the major products $\ce{P}$ and $\ce{S}$.

Consider the following reaction sequence:

$\text{Compound \textbf{A} (3,5-dimethyl-4-nitrobenzamide)} \xrightarrow[\Delta]{\ce{Br2 (1 eq.) / NaOH}} \textbf{B}$ $\textbf{B} \xrightarrow{\ce{Sn / HCl}} \xrightarrow{\ce{NaOH (aq)}} \textbf{C}$ $\textbf{C} \xrightarrow[\text{Pyridine, } 0^\circ\text{C}]{\ce{CH3COCl} \text{ (1 eq.)}} \textbf{D} \text{ (Major Product)}$

Identify the IUPAC name of the major product \textbf{D}.

Consider the following two independent reaction sequences aimed at synthesizing sterically hindered primary amines:

\textbf{Reaction I:} Potassium phthalimide + 2-Bromo-2-phenylpropane $\xrightarrow{\text{DMF}, 353\text{ K}}$ Major nitrogen-containing product $P$ + Major non-nitrogenous organic product $Q$

\textbf{Reaction II:} 2-Methyl-2-phenylpropanamide $\xrightarrow{\text{Br}_2, \text{NaOH(aq)}, 343\text{ K}}$ Major organic product $R$

Identify $P$, $Q$, and $R$.

Compound $\textbf{X}$ is 5-oxohexanamide. $\textbf{X}$ is treated with $\ce{Br2}$ (1 equivalent) and $\ce{NaOH}$ (4 equivalents) in an aqueous medium. The reaction mixture is initially kept at $273\text{ K}$ and then heated to $343\text{ K}$ to yield an intermediate $\textbf{Y}$. Under the reaction conditions, $\textbf{Y}$ spontaneously undergoes intramolecular cyclization with the loss of a water molecule to form the major product $\textbf{Z}$. Identify the major product $\textbf{Z}$.

An organic compound \textbf{X} (4-methylbenzamide) is treated with \ce{Br2 (l)} and \ce{NaOH (aq)} to form intermediate \textbf{Y}. Due to improper thermal regulation during the highly exothermic neutralization and subsequent addition of \ce{NaNO2 (aq)} and \ce{HCl (aq)}, the reaction mixture temperature reaches $40^\circ\text{C}$, yielding product \textbf{Z}. Finally, \textbf{Z} is treated with a freshly prepared solution of 4-nitrobenzenediazonium chloride \ce{(aq)} in an aqueous buffer of pH 9.5 to form the major product \textbf{W}. Identify the structure of \textbf{W}.

Consider the enantiomerically pure compound \ce{X}, (2S)-2-(4-nitrophenyl)propanamide. \ce{X} is subjected to two distinct reaction sequences:

Sequence 1: \ce{X} is treated with \ce{Br2} (1 eq.) and aqueous \ce{NaOH} at $70^\circ\text{C}$. The resulting intermediate is then reacted with \ce{SnCl2 / HCl} followed by neutralization with excess \ce{NaOH} to yield the major product \ce{P}.

Sequence 2: \ce{X} is treated with \ce{B2H6} in THF, followed by acidic workup and subsequent neutralization to yield the major product \ce{Q}.

Identify the correct IUPAC names and stereochemical descriptors for products \ce{P} and \ce{Q}.

An organic compound $\mathbf{P}$ (\ce{C8H8Cl2}) is treated with one equivalent of potassium phthalimide in DMF, followed by heating with hydrazine hydrate, to yield compound $\mathbf{Q}$ (\ce{C8H10ClN}) as the major product.

Compound $\mathbf{Q}$ gives a foul-smelling gas when heated with \ce{CHCl3} and alcoholic \ce{KOH}, but does \textbf{not} produce a red dye when treated with \ce{NaNO2}/\ce{HCl} at $0-5^\circ\text{C}$ followed by alkaline 2-naphthol. Instead, the reaction of $\mathbf{Q}$ with \ce{NaNO2}/\ce{HCl} at $0-5^\circ\text{C}$ evolves a colorless gas and forms compound $\mathbf{S}$.

Compound $\mathbf{S}$ does \textbf{not} yield a yellow precipitate upon treatment with \ce{I2} and \ce{NaOH}. Vigorous oxidation of $\mathbf{S}$ with acidic \ce{KMnO4} yields 4-chlorobenzoic acid.

Identify the structure of $\mathbf{P}$.

A primary alkyl halide $X$ ($\ce{C5H11Br}$) is treated with potassium phthalimide in $N,N$-dimethylformamide (DMF) at $353\text{ K}$. The reaction fails to yield the expected $N$-alkylphthalimide. However, when $X$ is heated with aqueous $\ce{AgNO3}$, it forms a pale yellow precipitate and yields an alcohol $Y$. Alcohol $Y$ produces immediate turbidity upon treatment with Lucas reagent ($\ce{ZnCl2}$ / conc. $\ce{HCl}$). Identify $X$ and the primary kinetic barrier preventing its reaction with potassium phthalimide.

An optically active primary amine $\textbf{Q}$ ($\ce{C8H11N}$) with an $(R)$-configuration is synthesized in high yield from an amide $\textbf{P}$ using $\ce{Br2 / KOH}$ at $343\text{ K}$. An attempt to synthesize $\textbf{Q}$ via the Gabriel phthalimide synthesis using the appropriate chiral alkyl bromide $\textbf{R}$ and potassium phthalimide in DMF at $373\text{ K}$ fails, yielding a hydrocarbon $\textbf{S}$ ($\ce{C8H8}$) as the major product. Identify $\textbf{P}$, $\textbf{R}$, and $\textbf{S}$.

Consider the optically active alcohol $\textbf{P}$, which is $(2R, 3S)$-3-phenylbutan-2-ol. $\textbf{P}$ undergoes two distinct reaction sequences to form primary amines $\textbf{R}$ and $\textbf{T}$:

$\textbf{Sequence 1:}$

1. $\textbf{P} \xrightarrow{\text{Phthalimide, } PPh_3\text{, DEAD}} \textbf{Q}$
2. $\textbf{Q} \xrightarrow{NH_2NH_2\text{, EtOH, }\Delta} \textbf{R}$

$\textbf{Sequence 2:}$

1. $\textbf{P} \xrightarrow{SOCl_2\text{, Pyridine}} \textbf{S}$
2. $\textbf{S} \xrightarrow{\text{Excess } NH_3\text{ (aq), sealed tube, } 373\text{ K}} \textbf{T}$ (Major primary amine)

Which of the following statements correctly describes the stereochemical relationship between $\textbf{R}$ and $\textbf{T}$?

An organic compound, 2-bromopropanal, is treated with one equivalent of Potassium phthalimide in N,N-dimethylformamide (DMF) at $350 \text{ K}$. Instead of the expected nucleophilic substitution, the reaction predominantly yields a volatile liquid $\mathbf{Y}$ that exhibits a strong IR absorption at $1690 \text{ cm}^{-1}$ and rapidly decolorizes a solution of $\ce{Br2}$ in $\ce{CCl4}$. Identify the major product $\mathbf{Y}$.

An unknown amine $\mathbf{X}$ with the molecular formula \ce{C4H11N} is subjected to a series of qualitative tests. I. $\mathbf{X}$ reacts with \ce{CHCl3} and ethanolic \ce{KOH} at $343 \text{ K}$ to produce a highly offensive-smelling compound $\mathbf{Y}$. II. $\mathbf{X}$ reacts with benzenesulfonyl chloride (\ce{PhSO2Cl}) to form a crystalline solid $\mathbf{Z}$. III. Surprisingly, solid $\mathbf{Z}$ is found to be completely insoluble in $10\% \text{ NaOH(aq)}$ at $298 \text{ K}$, despite $\mathbf{X}$ passing test I. Which of the following correctly identifies $\mathbf{X}$ and the primary chemical reason for the anomalous behavior in Test III?

Compound $\mathbf{X}$ is 4-aminobenzylamine. It is subjected to the following reaction sequence:

1. $\mathbf{X} \xrightarrow[\text{0-5}^\circ\text{C}]{\text{NaNO}_2 \text{ (1 eq.), dil. HCl (excess)}} \mathbf{Y}$
2. $\mathbf{Y} \xrightarrow[\text{0-5}^\circ\text{C}]{\beta\text{-naphthol, NaOH (excess)}} \mathbf{Z}$
3. $\mathbf{Z} \xrightarrow{\text{CHCl}_3\text{, KOH, }\Delta} \mathbf{W} \text{ (Major Product)}$

Identify the correct IUPAC name for the major product $\mathbf{W}$.

An alkyl halide $X$ (\ce{C7H7Cl}) can be converted to an amine via two pathways:

Pathway A: Heating $X$ with ethanolic \ce{NH3} in a sealed tube at 373 K yields a mixture of amines. The major secondary amine impurity formed is $Z$.

Pathway B: Phthalimide is treated with \ce{KOH} (alc.) to form a salt, which is then reacted with $X$ in DMF. The resulting intermediate is completely hydrolyzed with aqueous \ce{KOH} under heating to yield a pure primary amine $Y$ and a dicarboxylate salt.

$Y$ obtained from Pathway B is subjected to the Carbylamine test using \ce{CHCl3} and alcoholic \ce{KOH}, yielding a foul-smelling compound $W$.

Let $n_1$ be the total number of moles of \ce{KOH} consumed to convert 1 mole of phthalimide to 1 mole of $W$ via Pathway B and the subsequent Carbylamine test. Let $n_2$ be the number of $\pi$ bonds in compound $W$. Let $n_3$ be the number of $\pi$ bonds in compound $Z$.

Calculate the value of $(n_1 \times n_2) + n_3$.

Compound \textbf{X} (1-(tert-butyl)-2,4-dinitrobenzene) is subjected to the following reaction sequence:

1. \ce{Sn / HCl}, $\Delta$, followed by neutralization with aqueous \ce{NaOH} to yield Compound \textbf{Y}.
2. Compound \textbf{Y} is treated with exactly one equivalent of \ce{CHCl3} and excess ethanolic \ce{KOH} at elevated temperature to yield Compound \textbf{Z} as the major product.

Identify the correct IUPAC name of Compound \textbf{Z}.

Compound $\mathbf{X}$ has the molecular formula $C_{19}H_{17}N$. Its IR spectrum exhibits two distinct, sharp absorption bands in the $3300-3500\ \text{cm}^{-1}$ region. When $\mathbf{X}$ is subjected to the Hinsberg test using benzenesulfonyl chloride ($\ce{PhSO2Cl}$) in excess aqueous $\ce{NaOH}$ at 298 K, a biphasic mixture is observed with an insoluble organic layer. Separation of this organic layer followed by treatment with dilute aqueous $\ce{HCl}$ results in its complete dissolution, yielding a clear solution. Which of the following correctly identifies $\mathbf{X}$ and the primary reason for its anomalous Hinsberg behavior?

Separate samples of the following eight amines are subjected to the Hinsberg test using an excess of benzenesulfonyl chloride ($\ce{PhSO2Cl}$) and 10% aqueous $\ce{KOH}$ at 298 K.

(I) $n$-Dodecylamine (II) 2,2,2-Trifluoroethylamine (III) N-Phenylglycine (IV) N-Methylaniline (V) L-Proline (VI) Aniline (VII) N,N-Dimethylaniline (VIII) Diethylamine

How many of these amines yield a final product (or remain as a species) that is completely soluble in the aqueous alkaline layer?

An aqueous solution of L-Alanine ($pK_{a1} = 2.34$, $pK_{a2} = 9.69$, $pI = 6.01$) is subjected to two separate experiments at 298 K:

Experiment I: Treated with excess benzenesulfonyl chloride ($PhSO_2Cl$) in an aqueous buffer at pH = 4.0. Experiment II: Treated with excess $PhSO_2Cl$ in aqueous $NaOH$ (pH = 12.0), followed by careful acidification to pH = 1.0.

Identify the major organic species recovered from the amino acid in Experiment I and Experiment II, respectively.

Consider the reaction of the following four amines with benzenesulfonyl chloride (Hinsberg reagent) in aqueous $NaOH$ at $298\text{ K}$: (I) Cyclohexylamine (II) Aniline (III) 4-Nitroaniline (IV) 2-Nitroaniline Let $k_1, k_2, k_3,$ and $k_4$ be their respective initial rate constants for the nucleophilic attack on the sulfur atom. Which of the following correctly represents the decreasing order of their rate constants, and what is the primary chemical rationale for the slowest reacting species?

Aniline is treated with a nitrating mixture (conc. \ce{HNO3} and conc. \ce{H2SO4}) at 288 K, yielding three mononitrated products $X$, $Y$, and $Z$ with approximate yields of $51\%$, $47\%$, and $2\%$ respectively. Product $Y$ is isolated and subjected to the following sequence of reactions:

1. \ce{NaNO2 / HCl}, 273 K
2. \ce{HBF4}, followed by $\Delta$
3. \ce{Sn / HCl}, followed by \ce{NaOH (aq)}
4. Excess \ce{Br2 (aq)}

Identify the final product formed and the key species whose formation dictates the $47\%$ yield of $Y$ in the initial nitration step.

An amount of $12.1 \text{ g}$ of benzamide ($\ce{C6H5CONH2}$) undergoes Hofmann bromamide degradation with a $75\%$ yield to produce an aromatic amine, $\mathbf{A}$. The obtained sample of $\mathbf{A}$ is divided into two equal portions, Portion I and Portion II.

Portion I is treated with excess bromine water at $298 \text{ K}$ to yield compound $\mathbf{B}$ quantitatively.

Portion II is first protected using acetic anhydride in the presence of pyridine, then treated with $\ce{Br2}$ in acetic acid at $298 \text{ K}$, and finally subjected to acidic hydrolysis to yield the major mono-substituted product $\mathbf{C}$ quantitatively.

Assuming $100\%$ yield for all steps involving the conversion of $\mathbf{A}$ to $\mathbf{B}$ and $\mathbf{C}$, what is the total mass of bromine atoms incorporated into the final isolated products $\mathbf{B}$ and $\mathbf{C}$ combined? (Molar mass: Benzamide $= 121 \text{ g/mol}$, $\ce{Br} = 80 \text{ g/mol}$)

Consider the azo coupling reactions of 3-aminophenol with benzenediazonium chloride ($\ce{PhN2+Cl-}$) under two different pH conditions at $273-278\text{ K}$:

Reaction I: 3-aminophenol + $\ce{PhN2+Cl-} \xrightarrow{\text{pH} = 4.5}$ Major Product $\mathbf{P}$

Reaction II: 3-aminophenol + $\ce{PhN2+Cl-} \xrightarrow{\text{pH} = 9.5}$ Major Product $\mathbf{Q}$

Identify the correct IUPAC names for the major products $\mathbf{P}$ and $\mathbf{Q}$.

Consider the following aromatic amines in aqueous medium at 298 K: (I) Aniline (II) 2-Methylaniline (III) $N,N$-Dimethylaniline (IV) $N,N,2$-Trimethylaniline

Let $\Delta pK_{b1} = pK_b(\text{I}) - pK_b(\text{II})$ and $\Delta pK_{b2} = pK_b(\text{III}) - pK_b(\text{IV})$.

Furthermore, compounds III and IV are independently treated with Benzenediazonium chloride (\ce{PhN2+Cl-}) at pH 6 and 273 K. Compound III yields a highly colored azo dye, whereas compound IV yields product Y.

Which of the following correctly identifies the signs of $\Delta pK_{b1}$ and $\Delta pK_{b2}$, and the identity of product Y?

Consider the following multi-step synthesis:

$\text{4-Nitrotoluene} \xrightarrow{Br_2, Fe} \text{P}$

$\text{P} \xrightarrow{Sn, HCl} \xrightarrow{NaOH(aq)} \text{Q}$

$\text{Q} \xrightarrow{NaNO_2, \text{dil. } HCl, H_2O, 298\text{ K}} \text{R}$

$\text{R} \xrightarrow{CHCl_3, aq. NaOH, 343\text{ K}} \xrightarrow{H_3O^+} \text{S (Major Product)}$

Identify the major product \textbf{S}.

Benzenediazonium chloride ($\ce{PhN2+Cl-}$) is synthesized at $273\text{ K}$. It is then subjected to three distinct reaction conditions to test chemoselectivity and stability:

Condition I: The diazonium salt is added to an aqueous solution of phenol at $\text{pH} = 0.5$ and the mixture is allowed to warm to $298\text{ K}$. The major organic product isolated is $\mathbf{X}$.

Condition II: The diazonium salt is added to an equimolar mixture of phenol and aniline, strictly buffered at $\text{pH} = 9.5$ at $273\text{ K}$. The major organic product isolated is $\mathbf{Y}$.

Condition III: The diazonium salt is added to an equimolar mixture of phenol and aniline, strictly buffered at $\text{pH} = 4.5$ at $273\text{ K}$. The major organic product isolated is $\mathbf{Z}$.

Identify $\mathbf{X}$, $\mathbf{Y}$, and $\mathbf{Z}$.

Consider the following reaction sequence starting with ethyl 3-methyl-4-nitrobenzoate:

$\text{Ethyl 3-methyl-4-nitrobenzoate} \xrightarrow[ \text{2. } NaOH(aq) ]{ \text{1. } Sn / HCl, \Delta } \mathbf{P}$

$\mathbf{P} \xrightarrow{ NaNO_2 / HCl, H_2O, 298\text{ K} } \mathbf{Q}$

$\mathbf{Q} \xrightarrow[ \text{2. } H_3O^+ ]{ \text{1. Excess } LiAlH_4, \text{ dry ether} } \mathbf{R}$

Identify the major organic product $\mathbf{R}$.

Consider three isomeric amines $\mathbf{A}$, $\mathbf{D}$, and $\mathbf{F}$ with the molecular formula $\ce{C7H9N}$.

1. $\mathbf{A}$ cannot be prepared by Gabriel phthalimide synthesis. It reacts with Hinsberg's reagent to form a precipitate insoluble in aqueous $\ce{NaOH}$. Treatment of $\mathbf{A}$ with $\ce{NaNO2/HCl}$ at $273\text{ K}$ yields a yellow oil $\mathbf{C}$.
2. $\mathbf{D}$ can be prepared by Gabriel phthalimide synthesis. Treatment of $\mathbf{D}$ with $\ce{NaNO2/HCl}$ at $273\text{ K}$ produces brisk effervescence of a diatomic gas and a major organic product $\mathbf{E}$.
3. $\mathbf{F}$ cannot be prepared by Gabriel phthalimide synthesis, but its Hinsberg product is completely soluble in aqueous $\ce{NaOH}$. Treatment of $\mathbf{F}$ with $\ce{NaNO2/HCl}$ at $273\text{ K}$ yields a water-soluble salt $\mathbf{G}$ which does not evolve gas. Warming the aqueous solution of $\mathbf{G}$ to $298\text{ K}$ yields $\mathbf{H}$.

Identify $\mathbf{C}$, $\mathbf{E}$, and $\mathbf{H}$ (assuming $\mathbf{F}$ is the para-isomer).

An industrial synthesis of a specialized azo dye requires the preparation of benzenediazonium chloride from $N$-phenylacetamide.

Step 1: $0.4\text{ mol}$ of $N$-phenylacetamide undergoes complete nucleophilic acyl substitution (hydrolysis) in aqueous $\ce{HCl}$ at $363\text{ K}$. The resulting aqueous mixture has a total heat capacity $C_{p1} = 2.0\text{ kJ K}^{-1}$.

Step 2: To shift the basicity-solvation competition and accelerate nitrosation, $500\text{ g}$ of $N,N$-dimethylformamide (DMF, specific heat capacity $s = 2.0\text{ J g}^{-1}\text{ K}^{-1}$) initially at $293\text{ K}$ is added to the hot mixture.

Step 3: The aprotic nature of DMF deprives the diazonium cation of hydrogen-bond stabilization, drastically lowering the activation barrier for $\ce{N2}$ loss. To prevent decomposition, the mixture is cooled to exactly $273\text{ K}$ by adding solid ice (at $273\text{ K}$).

Step 4: $0.4\text{ mol}$ of $\ce{NaNO2}$ is added, and diazotization ($\Delta H_{rxn} = -125\text{ kJ mol}^{-1}$) goes to completion at $273\text{ K}$.

Assuming no heat exchange with the surroundings and that the melted ice remains at $273\text{ K}$, calculate the total mass of ice required to achieve the cooling and maintain the system strictly at $273\text{ K}$ during the entire process.

(Given: $\Delta H_{fusion}$ of ice = $6.0\text{ kJ mol}^{-1}$, Molar mass of $\ce{H2O}$ = $18\text{ g mol}^{-1}$)

Aniline ($\ce{C6H5NH2}$) is treated with $\ce{NaNO2}$ and aqueous $\ce{HCl}$ at $298\text{ K}$. The resulting reaction mixture is immediately divided into two equal portions, I and II. Portion I is treated with $\ce{CuCl}$ and $\ce{HCl}$. Portion II is treated with $\ce{Cu}$ powder and $\ce{HCl}$. Let the major organic products isolated from Portion I and Portion II be $P_1$ and $P_2$, respectively. Identify $P_1$ and $P_2$.

A chemist attempts to synthesize a haloarene using the following reaction sequence:

\begin{align*} \text{Step 1: } & \ce{C6H5NH2} \xrightarrow[\text{Pyridine}]{\ce{PhSO2Cl} \text{ (1.0 eq)}} \textbf{P} \ \text{Step 2: } & \textbf{P} \xrightarrow{\ce{Br2}, \ce{FeBr3}} \textbf{Q} \text{ (Major)} \ \text{Step 3: } & \textbf{Q} \xrightarrow[\Delta]{\ce{H3O+}} \textbf{R} \ \text{Step 4: } & \textbf{R} \text{ (2.0 eq)} \xrightarrow[\text{273 K}]{\ce{NaNO2} \text{ (1.0 eq)}, \ce{HCl} \text{ (1.0 eq)}} \textbf{S} \text{ (Major)} \end{align*}

Identify the major organic product \textbf{S}.

Benzene undergoes electrophilic aromatic substitution with \ce{Cl_2 / FeCl_3} to give \textbf{A}, which upon nitration with a mixture of conc. \ce{HNO_3} and conc. \ce{H_2SO_4} yields \textbf{P} as the major isomer. \textbf{P} is then subjected to two different reaction pathways:

\textbf{Pathway 1:}

1. \ce{Sn / HCl}, then \ce{NaOH(aq)} $\rightarrow$ \textbf{Q}
2. \ce{NaNO_2 / HCl}, $273-278\text{ K}$ $\rightarrow$ \textbf{R}
3. \ce{CuCN / KCN}, $\Delta$ $\rightarrow$ \textbf{S}
4. \ce{CH_3MgBr}, dry ether, then \ce{H_3O^+}, $\Delta$ $\rightarrow$ \textbf{T}

\textbf{Pathway 2:}

1. \ce{LiAlH_4} (excess), dry ether, $\Delta$, then \ce{H_2O} $\rightarrow$ \textbf{U}

Identify the major products \textbf{T} and \textbf{U}.

Compound $\textbf{X}$ is prepared by treating $p$-nitroaniline with $NaNO_2$ and aqueous $HCl$ at $273\text{ K}$. The resulting cold solution of $\textbf{X}$ is immediately added to a reaction vessel containing an equimolar mixture of $CuCl$ and $N,N$-dimethylaniline. The reaction medium is carefully buffered at $\text{pH} = 4.5$ and maintained at $273\text{ K}$. Which of the following is the major product $\textbf{Y}$ formed?

Consider the azo coupling reactions of $N,N$-dimethylaniline (\textbf{P}) and $2$-methyl-$N,N$-dimethylaniline (\textbf{Q}) with benzenediazonium chloride (\ce{PhN2+ Cl-}) at $273\text{ K}$ in an aqueous buffer of $\text{pH} = 4.5$. Which of the following statements correctly describes the outcome and the underlying chemical principles governing the reactivity of \textbf{P} and \textbf{Q}?

Consider the reaction of \ce{1-(4-hydroxyphenyl)-4,4,4-trifluorobutane-1,3-dione} with one equivalent of benzenediazonium chloride (\ce{PhN2+ Cl-}) in an aqueous buffer at $pH = 9$ and $0^\circ C$. Identify the major product formed.

Compound \ce{P} ($C_8H_{11}N$) is an aromatic amine that yields 2,6-dimethylphenol upon diazotization followed by heating with water. \ce{P} is subjected to the following two parallel reaction sequences:

Sequence 1: \ce{P} $\xrightarrow{\ce{CH_3I} \text{ (2 eq.)}, \ce{Na_2CO_3}}$ \ce{Q} $\xrightarrow{\text{4-nitrobenzenediazonium chloride, pH 4-5, } 0^\circ C}$ \ce{R}

Sequence 2: \ce{P} $\xrightarrow{\ce{NaNO_2}, \ce{HCl}, 0^\circ C} \xrightarrow{\ce{CuCN}, \ce{KCN}}$ \ce{S} $\xrightarrow{\ce{DIBAL-H}, -78^\circ C} \xrightarrow{\ce{H_2O}}$ \ce{T}

Identify the major products \ce{R} and \ce{T}.

Consider the polyfunctional compound $X$, Ethyl 3,3,5-trimethyl-5-nitro-2-oxohexanoate. $X$ is subjected to two different reduction sequences:

Sequence 1: $X \xrightarrow{\text{Sn/HCl, } \Delta} \xrightarrow{\text{NaOH (aq), cold}} P$ (Major Product) Sequence 2: $X \xrightarrow{\text{LiAlH}_4 \text{ (excess), THF}} \xrightarrow{H_3O^+} Q$ (Major Product)

Assuming no ester hydrolysis occurs in Sequence 1, identify the major products $P$ and $Q$.

An organic compound \textbf{X} (3-methyl-4-nitrophenyl acetate) is treated with excess \ce{LiAlH4} in THF followed by aqueous workup to yield an aromatic compound \textbf{Y} and a volatile aliphatic alcohol. Compound \textbf{Y} is then subjected to the Hinsberg test using excess benzenesulfonyl chloride (\ce{PhSO2Cl}) in aqueous \ce{NaOH} at 298 K, yielding \textbf{W} as the major organic product. Which of the following statements correctly identifies the structure of \textbf{W} and its physical state in the alkaline reaction mixture?

Consider the compound $\textbf{X}$, which is 2,4,6-tri-\textit{tert}-butylnitrobenzene. Reaction 1: $\textbf{X}$ is treated with excess $\ce{LiAlH4}$ in dry ether at reflux to yield major product $\textbf{P}$. Reaction 2: $\textbf{X}$ is treated with $\ce{Sn/HCl}$ followed by aqueous $\ce{NaOH}$ to yield major product $\textbf{Q}$. Identify $\textbf{P}$, $\textbf{Q}$, and the correct relationship between the basicity constant ($K_b$) of $\textbf{Q}$ and aniline.

Consider the substrate \textbf{X}, ethyl 4-(bromomethyl)benzoate ($p\text{-BrCH}_2\text{-C}_6\text{H}_4\text{-COOCH}_2\text{CH}_3$). Three different synthetic pathways are employed to convert the bromomethyl group into a primary amine:

\textbf{Pathway 1:} \textbf{X} is reacted with potassium phthalimide in DMF, followed by refluxing with excess hydrazine ($\text{NH}_2\text{NH}_2$) in ethanol to yield major product \textbf{P}.

\textbf{Pathway 2:} \textbf{X} is reacted with $\text{NaN}_3$ in DMF, followed by catalytic hydrogenation ($\text{H}_2$, $\text{Pd/C}$) at 298 K to yield major product \textbf{Q}.

\textbf{Pathway 3:} \textbf{X} is reacted with $\text{AgNO}_2$ to isolate the major aliphatic nitro compound, which is subsequently treated with excess $\text{LiAlH}_4$ in THF followed by aqueous workup to yield major product \textbf{R}.

Identify the major products \textbf{P}, \textbf{Q}, and \textbf{R}.

An equimolar mixture of pure (S)-2-bromobutane and ammonia is heated in a sealed tube. Due to the +I effect, the initially formed primary amine is kinetically superior to ammonia as a nucleophile, leading to a Hofmann ammonolysis cascade. The major secondary amine \textbf{X} produced in this cascade is isolated. \textbf{X} is then subjected to nucleophilic acyl substitution with excess acetyl chloride in pyridine to yield amide \textbf{Y}. Assuming all substitutions at chiral centers proceed exclusively via the $S_N2$ mechanism, which of the following represents the correct stereochemical designation of \textbf{Y}?

Compound $\mathbf{A}$ ($\ce{C9H10Br2}$) is treated with 1 equivalent of potassium phthalimide in DMF at $350\text{ K}$, followed by heating with aqueous $\ce{NaOH}$ to yield compound $\mathbf{B}$ ($\ce{C9H12BrN}$). Compound $\mathbf{B}$ is then treated with $\ce{NaNO2}$ and $\ce{HCl}$ at $273\text{ K}$, followed by the addition of phenol in dilute $\ce{NaOH}$. No azo dye is formed; instead, a clear solution with the evolution of a colorless gas is observed, yielding compound $\mathbf{C}$ ($\ce{C9H11BrO}$) as the major organic product. Compound $\mathbf{C}$ on vigorous oxidation with acidic $\ce{KMnO4}$ yields a monobasic acid $\mathbf{D}$ ($\ce{C7H5BrO2}$). Identify the correct structure of starting material $\mathbf{A}$.

Consider the ammonolysis of methyl iodide in an aqueous solvent system at $298\text{ K}$, which sequentially generates primary ($1^\circ$), secondary ($2^\circ$), and tertiary ($3^\circ$) methylamines. The thermodynamic basicity of these amines in the aqueous phase exhibits a stark deviation from their intrinsic gas-phase proton affinities. Let $pK_{b1}$, $pK_{b2}$, and $pK_{b3}$ denote the base dissociation constants (expressed as $pK_b$) for the $1^\circ$, $2^\circ$, and $3^\circ$ amines, respectively. Which of the following options correctly establishes the sequence of $pK_b$ values and accurately identifies the dominant thermodynamic factor responsible for the anomalous position of the $3^\circ$ amine?