Comprehensive Study Notes on Amines

Structure, Classification, and Nomenclature of Amines

• Definition and Occurrence:

  • Amines are organic compounds derived by replacing one or more hydrogen atoms of an ammonia ($NH_3$) molecule with alkyl or aryl group(s).

  • Amines occur naturally in proteins, vitamins, alkaloids, and hormones.

• Biological Importance and Synthetic Applications:

  • Adrenaline and Ephedrine: Contain a secondary amino group ($-NH-$); used to increase blood pressure.

  • Novocain: A synthetic amino compound used as a local anaesthetic in dentistry.

  • Benadryl: A well-known antihistamine drug containing a tertiary amino group ($-N(R)_2$).

  • Quaternary Ammonium Salts: Extensively used as surface-active agents (surfactants).

  • Diazonium Salts: Key intermediates in the synthetic preparation of various aromatic compounds, including synthetic dyes.

• Classification of Amines:

  • Amines are classified into primary ($1^\circ$), secondary ($2^\circ$), or tertiary ($3^\circ$) based on the number of hydrogen atoms replaced in the ammonia molecule:

  • Primary Amines ($1^\circ$): Formed by replacing one hydrogen atom of $NH_3$ ($R-NH_2$). Contains the functional group $-NH_2$ (amino group).

  • Secondary Amines ($2^\circ$): Formed by replacing two hydrogen atoms of $NH_3$ ($R_2NH$ or $R-NH-R'$). Contains the functional group $-NH-$ (imino group).

  • Tertiary Amines ($3^\circ$): Formed by replacing all three hydrogen atoms of $NH_3$ ($R_3N$ or $R-N(R')-R''$).

  • The substituent $R$ can be an alkyl or aryl group.

• Structure of Amines:

  • The nitrogen atom of an amine is trivalent and carries an unshared pair (lone pair) of electrons, similar to ammonia.

  • Nitrogen orbitals are $sp^3$ hybridised.

  • Three of the $sp^3$ hybrid orbitals overlap with orbitals of hydrogen or carbon atoms to form three $\sigma$ bonds.

  • The fourth $sp^3$ hybrid orbital contains the unshared lone pair of electrons.

  • Due to the presence of the unshared electron pair, the bond angle is decreased from the ideal tetrahedral angle ($109.5^\circ$).

  • Example: In trimethylamine ($(CH_3)_3N$), the $C-N-C$ bond angle is $108^\circ$.

  • Shape: Pyramidal geometry.

• Nomenclature of Aliphatic Amines:

  • Common System:

  • Named by prefixing the alkyl group name to "amine" (e.g., Alkylamine).

  • Primary Amines: $CH_3NH_2$ is named Methylamine.

  • Secondary and Tertiary Amines:

    • If groups are identical, prefixes "di" or "tri" are used before the alkyl group name. E.g., $CH_3-NH-CH_3$ is Dimethylamine; $(CH_3)_3N$ is Trimethylamine.

    • If groups are different, alkyl groups are named in alphabetical order followed by "amine". E.g., $CH_3-NH-C_2H_5$ is Ethylmethylamine; $CH_3-N(C_2H_5)-CH_2CH_2CH_3$ is Ethyl methyl propyl amine.

  • IUPAC System:

  • Primary Amines: Named as Alkanamines by replacing the terminal 'e' of the parent alkane name with 'amine' (e.g., $CH_3NH_2$ is Methanamine).

  • Secondary and Tertiary Amines: Specified using the prefix $N$-alkyl or $N,N$-dialkyl before the alkanamine parent chain (e.g., $CH_3-NH-C_2H_5$ is $N$-Methylethanamine; $CH_3-N(CH_3)_2$ is $N,N$-Dimethylmethanamine).

  • Polyamines: If more than one amino group is present at different positions, the 'e' of the alkane name is retained, and prefixes such as 'diamine' or 'triamine' are added with locants (e.g., $H_2N-CH_2-CH_2-NH_2$ is Ethane-1,2-diamine).

• Nomenclature of Aromatic Amines:

  • In IUPAC, $C_6H_5NH_2$ is named Benzenamine or Aniline (accepted by IUPAC).

  • Common name for $C_6H_5NH_2$ is Aniline.

  • $o\text{-Toluidine}$ is named $2\text{-Methylaniline}$ (or $2\text{-Methylbenzenamine}$).

  • $o\text{-Bromoaniline}$ is named $2\text{-Bromoaniline}$ (or $2\text{-Bromobenzenamine}$).

  • $C_6H_5N(CH_3)_2$ is named $N,N\text{-Dimethylaniline}$.

Methods of Preparation of Amines

• 1. Reduction of Nitro Compounds:

  • Catalytic Hydrogenation: Pass hydrogen gas ($H_2$) in the presence of finely divided metals such as Nickel ($Ni$), Palladium ($Pd$), or Platinum ($Pt$) in ethanol:     $R-NO_2 + 3H_2 \xrightarrow{Pd\,/\,\text{Ethanol}} R-NH_2 + 2H_2O$

  • Chemical Reduction: Reduction with metals in an acidic medium:     $Ar-NO_2 \xrightarrow{Sn + HCl \text{ or } Fe + HCl} Ar-NH_2$

  • Preference of Reagent: Reduction with iron scrap ($Fe$) and hydrochloric acid ($HCl$) is preferred over tin ($Sn$) and $HCl$ because the $FeCl_2$ produced hydrolyses to release $HCl$ during the reaction. Thus, only a small quantity of $HCl$ is required to initiate the process.

• 2. Ammonolysis of Alkyl Halides:

  • Alkyl or benzyl halides react with an ethanolic solution of ammonia ($NH_3$) in a sealed tube at $373\,K$ via nucleophilic substitution.

  • The process of cleavage of the $C-X$ bond by an ammonia molecule is defined as ammonolysis:     $NH_3 + R-X \rightarrow R-NH_3^+ X^- \xrightarrow{NH_3} R-NH_2 + NH_4^+ X^-$

  • The primary amine formed acts as a nucleophile and reacts further with alkyl halide to form secondary, tertiary amines, and quaternary ammonium salts:     $R-NH_2 \xrightarrow{R-X} R_2NH \xrightarrow{R-X} R_3N \xrightarrow{R-X} R_4N^+ X^-$

  • Free Amine Regeneration: Free amine is obtained from the ammonium salt by treatment with a strong base:     $R-NH_3^+ X^- + NaOH \rightarrow R-NH_2 + H_2O + NaX$

  • Disadvantage: Yields a mixture of $1^\circ$, $2^\circ$, $3^\circ$ amines and $4^\circ$ ammonium salts.

  • Optimization: Primary amine is obtained as the major product if a large excess of ammonia ($NH_3$) is used.

  • Order of Reactivity of Halides: $R-I > R-Br > R-Cl$.

• 3. Reduction of Nitriles:

  • Nitriles on reduction with Lithium Aluminium Hydride ($LiAlH_4$), catalytic hydrogenation ($H_2/Ni$), or sodium amalgam in ethanol ($Na(Hg) / C_2H_5OH$) yield primary amines:     $R-C\equiv N \xrightarrow{LiAlH_4 \text{ or } H_2/Ni \text{ or } Na(Hg)/C_2H_5OH} R-CH_2-NH_2$

  • Example: $CH_3-C\equiv N \xrightarrow{LiAlH_4} CH_3CH_2NH_2$ (Ethanenitrile to Ethanamine).

• 4. Reduction of Amides:

  • Amides on reduction with $LiAlH_4$ followed by hydrolysis yield primary amines with the same number of carbon atoms:     $R-CO-NH_2 \xrightarrow{(i)\,LiAlH_4 \,/\, (ii)\,H_2O} R-CH_2-NH_2$

  • Example: $CH_3CONH_2 \xrightarrow{(i)\,LiAlH_4 \,/\, (ii)\,H_2O} CH_3CH_2NH_2$ (Ethanamide to Ethanamine).

• 5. Gabriel Phthalimide Synthesis:

  • Specially used for the preparation of primary aliphatic amines.

  • Process:

  1. Phthalimide is treated with ethanolic Potassium Hydroxide ($KOH$) to form potassium phthalimide.

  2. Potassium phthalimide is heated with an alkyl halide ($R-X$) to yield $N$-alkylphthalimide.

  3. Alkaline hydrolysis of $N$-alkylphthalimide with aqueous $NaOH$ produces primary aliphatic amine and sodium phthalate.

  • Limitation: Aromatic primary amines cannot be prepared by this method because aryl halides do not undergo nucleophilic substitution with the phthalimide anion under normal conditions.

• 6. Hoffmann Bromamide Degradation Reaction:

  • Method for preparing primary aliphatic and aromatic amines from primary amides.

  • Amides are treated with bromine ($Br_2$) in an aqueous or ethanolic solution of Sodium Hydroxide ($NaOH$):     $R-CO-NH_2 + Br_2 + 4NaOH \rightarrow R-NH_2 + Na_2CO_3 + 2NaBr + 2H_2O$

  • Key Feature: The amine formed contains one carbon atom less than the parent amide.

  • Example: $CH_3CONH_2 + Br_2 + 4NaOH \rightarrow CH_3NH_2 + Na_2CO_3 + 2NaBr + 2H_2O$ (Ethanamide to Methanamine).

Physical Properties of Amines

• Physical State and Odour:

  • Lower aliphatic amines are gases with an unpleasant fishy odour.

  • Primary aliphatic amines containing three or more carbon atoms are liquids, while higher amines are solids.

  • Aniline and other arylamines are generally colourless but develop colour during storage due to atmospheric oxidation.

• Solubility:

  • Lower aliphatic amines are soluble in water because they form hydrogen bonds with water molecules.

  • Solubility decreases as the molar mass increases due to the increase in size of the hydrophobic alkyl part.

  • Higher amines are practically insoluble in water.

  • Amines are readily soluble in organic solvents such as alcohols, ethers, and benzene.

  • Alcohols have higher solubility in water than amines of comparable molecular mass because oxygen is more electronegative than nitrogen, making the $O-H$ bond more polar and capable of forming stronger hydrogen bonds with water than the $N-H$ bond in amines.

• Boiling Points:

  • Primary ($1^\circ$) and secondary ($2^\circ$) amines undergo intermolecular association due to hydrogen bonding between the nitrogen of one molecule and hydrogen of another.

  • Intermolecular hydrogen bonding is greater in $1^\circ$ amines than $2^\circ$ amines because $1^\circ$ amines have two hydrogen atoms available for H-bonding, whereas $2^\circ$ amines have only one.

  • Tertiary ($3^\circ$) amines do not undergo intermolecular H-bonding due to the absence of hydrogen atoms directly attached to the nitrogen atom.

  • Boiling point order of isomeric amines: $1^\circ \text{ amine} > 2^\circ \text{ amine} > 3^\circ \text{ amine}$.

  • Amines have lower boiling points than alcohols of comparable molecular mass because oxygen is more electronegative than nitrogen, making $O-H$ hydrogen bonds stronger than $N-H$ hydrogen bonds.

Basicity and Chemical Reactions of Amines

• Basicity of Amines:

  • Amines possess an unshared pair of electrons on the nitrogen atom, making them act as Lewis bases and nucleophiles.

  • Amines react with acids to form salts:     $R-NH_2 + HX \rightleftharpoons R-NH_3^+ X^-$

  • Amine salts are soluble in water but insoluble in organic solvents like ether. Treatment with a base ($NaOH$) regenerates the parent amine:     $R-NH_3^+ X^- + OH^- \rightarrow R-NH_2 + H_2O + X^-$

  • In aqueous solution, basic dissociation constant ($K_b$) and $pK_b$ are given by:     $R-NH_2 + H_2O \rightleftharpoons R-NH_3^+ + OH^-$     $K_b = \frac{[R-NH_3^+][OH^-]}{[R-NH_2]}$     $pK_b = -\log K_b$

  • A larger $K_b$ or a smaller $pK_b$ value indicates a stronger base.

• Alkanamines vs Ammonia:

  • Alkanamines are stronger bases than ammonia.

  • The electron-releasing alkyl group ($+I$ effect) pushes electron density toward nitrogen, making the lone pair more available for sharing with protons.

  • The resulting substituted ammonium cation is stabilized by the $+I$ effect of alkyl groups.

• Basicity in Gas Phase vs Aqueous Phase:

  • Gas Phase: Governed entirely by the $+I$ effect:     $\text{Order: } 3^\circ \text{ amine} > 2^\circ \text{ amine} > 1^\circ \text{ amine} > NH_3$

  • Aqueous Phase: Governed by a combination of three factors:

  1. Inductive Effect ($+I$ effect): $3^\circ > 2^\circ > 1^\circ$.

  2. Solvation Effect: Protonated amines are stabilized by H-bonding with water molecules, releasing hydration energy ($1^\circ > 2^\circ > 3^\circ$).

  3. Steric Factor: Crowding of alkyl groups hinders protonation and disrupts hydration ($1^\circ > 2^\circ > 3^\circ$).

  • Aqueous Basicity Trends:

  • For Methyl-substituted amines: $(CH_3)_2NH > CH_3NH_2 > (CH_3)_3N > NH_3$ ($2^\circ > 1^\circ > 3^\circ > NH_3$).

  • For Ethyl-substituted amines: $(C_2H_5)_2NH > (C_2H_5)_3N > C_2H_5NH_2 > NH_3$ ($2^\circ > 3^\circ > 1^\circ > NH_3$).

• Arylamines vs Ammonia:

  • Aromatic amines (like aniline) are far less basic than ammonia and aliphatic amines.

  • In aniline, the unshared electron pair on nitrogen is conjugated with the $\pi$-system of the benzene ring and delocalized over the ring, making it less available for protonation.

  • Aniline is stabilized by 5 resonance structures, whereas the anilinium ion ($C_6H_5NH_3^+$) has only 2 resonance structures. Thus, aniline has a lower tendency to accept a proton.

  • Effect of Substituents on Aromatic Amines:

  • Electron Releasing Groups (ERG) (e.g., $-OCH_3$, $-CH_3$): Increase basic strength by stabilizing the cation.

  • Electron Withdrawing Groups (EWG) (e.g., $-NO_2$, $-CN$, $-X$): Decrease basic strength by destabilizing the cation.

• Chemical Reactions:

  • 1. Alkylation:

  • Amines react with alkyl halides to form higher substituted amines:       $C_2H_5NH_2 \xrightarrow{C_2H_5I, -HI} (C_2H_5)_2NH \xrightarrow{C_2H_5I, -HI} (C_2H_5)_3N \xrightarrow{C_2H_5I} (C_2H_5)_4N^+ I^-$

  • 2. Acylation:

  • Primary and secondary amines react with acid chlorides, acid anhydrides, and esters by nucleophilic substitution to form amides.

  • Carried out in the presence of a base stronger than the amine (e.g., pyridine) to remove $HCl$:       $C_2H_5NH_2 + CH_3COCl \xrightarrow{\text{Pyridine}} C_2H_5NHCOCH_3 + HCl$       $C_6H_5NH_2 + (CH_3CO)_2O \xrightarrow{\text{Pyridine}} C_6H_5NHCOCH_3 + CH_3COOH$

  • 3. Benzoylation:

  • Reaction of amines with benzoyl chloride ($C_6H_5COCl$):       $CH_3NH_2 + C_6H_5COCl \xrightarrow{\text{Base}} CH_3NHCOC_6H_5 + HCl$ ($N$-Methylbenzamide).

  • 4. Carbylamine Reaction (Isocyanide Test):

  • Primary aliphatic and aromatic amines on heating with chloroform ($CHCl_3$) and ethanolic $KOH$ produce foul-smelling isocyanides (carbylamines):       $R-NH_2 + CHCl_3 + 3KOH \xrightarrow{\Delta} R-NC + 3KCl + 3H_2O$

  • Secondary and tertiary amines do NOT give this test.

  • 5. Reaction with Nitrous Acid ($HNO_2$):

  • Primary Aliphatic Amines: React with $HNO_2$ (prepared in situ from $NaNO_2 + HCl$) to form unstable diazonium salts, which decompose to evolve $N_2$ gas quantitatively and yield alcohols:       $R-NH_2 + HNO_2 \xrightarrow{NaNO_2 + HCl} [R-N_2^+ Cl^-] \xrightarrow{H_2O} R-OH + N_2 \uparrow + HCl$

  • Primary Aromatic Amines: React with $HNO_2$ at $273-278\,K$ to form stable arenediazonium salts:       $C_6H_5NH_2 + NaNO_2 + 2HCl \xrightarrow{273-278\,K} C_6H_5N_2^+ Cl^- + NaCl + 2H_2O$

  • 6. Reaction with Aryl Sulphonyl Chloride (Hinsberg's Reagent):

  • Benzene sulphonyl chloride ($C_6H_5SO_2Cl$) reacts differently with $1^\circ$, $2^\circ$, and $3^\circ$ amines:

    • Primary Amine: Forms $N$-alkyl benzene sulphonamide. Contains an acidic hydrogen on nitrogen, so it dissolves in aqueous alkali ($NaOH$).

    • Secondary Amine: Forms $N,N$-dialkyl benzene sulphonamide. Lacks hydrogen on nitrogen, so it is insoluble in alkali.

    • Tertiary Amine: Does NOT react with Hinsberg's reagent.

  • 7. Electrophilic Substitution Reactions of Aniline:

  • Bromination: Aniline reacts with bromine water at room temperature to give a white precipitate of 2,4,6-tribromoaniline:       $C_6H_5NH_2 + 3Br_2(aq) \rightarrow \text{2,4,6-Tribromoaniline} + 3HBr$       To obtain monobromo derivative (4-bromoaniline), $-NH_2$ is protected by acetylation with $(CH_3CO)_2O$ in pyridine to acetanilide, followed by bromination and subsequent hydrolysis.

  • Nitration: Direct nitration with conc. $HNO_3/H_2SO_4$ at $288\,K$ yields a mixture: 51% $p$-nitroaniline, 47% $m$-nitroaniline, and 2% $o$-nitroaniline. $m$-Nitroaniline forms in high yield because aniline is protonated in acidic medium to form the anilinium ion ($C_6H_5NH_3^+$), which is meta-directing. To obtain $p$-nitroaniline as the major product, the amino group is protected by acetylation prior to nitration.

  • Sulphonation: Aniline reacts with conc. $H_2SO_4$ to form anilinium hydrogen sulphate, which on heating at $453-473\,K$ rearranges to sulphanilic acid. Sulphanilic acid exists as a Zwitter ion ($^+H_3N-C_6H_4-SO_3^-$).

  • Friedel-Crafts Reaction Failure: Aniline does NOT undergo Friedel-Crafts reaction (alkylation or acylation) because it forms a salt with anhydrous $AlCl_3$ (Lewis acid catalyst). Nitrogen acquires a positive charge, acting as a strong deactivating group.

Diazonium Salts: Preparation, Reactions, and Synthetic Utility

• General Formula and Nomenclature:

  • General formula: $R-N_2^+ X^-$ where $R$ is an aryl group and $X^-$ is $Cl^-, Br^-, HSO_4^-, BF_4^-$, etc.

  • Named by adding the suffix "diazonium" to the parent hydrocarbon, followed by the anion name (e.g., $C_6H_5N_2^+ Cl^-$ is Benzenediazonium chloride).

• Stability:

  • Arenediazonium salts are relatively stable in solution at low temperatures ($273-278\,K$) due to resonance stabilization of the positive charge over the benzene ring.

  • Alkanediazonium salts are unstable and rapidly decompose to yield carbocations and $N_2$ gas.

• Method of Preparation (Diazotisation):

  • Prepared by reacting primary aromatic amines with nitrous acid ($NaNO_2 + HCl$) at $273-278\,K$ ($0-5^\circ C$):     $C_6H_5NH_2 + NaNO_2 + 2HCl \xrightarrow{273-278\,K} C_6H_5N_2^+ Cl^- + NaCl + 2H_2O$

• Chemical Reactions:

  • A. Replacement Reactions (Displacement of Nitrogen):

  • Sandmeyer Reaction:       $ArN_2^+ Cl^- \xrightarrow{Cu_2Cl_2 / HCl} ArCl + N_2$       $ArN_2^+ Cl^- \xrightarrow{Cu_2Br_2 / HBr} ArBr + N_2$       $ArN_2^+ Cl^- \xrightarrow{CuCN / KCN} ArCN + N_2$

  • Gattermann Reaction:       $ArN_2^+ X^- \xrightarrow{Cu / HCl} ArCl + N_2 + CuX$       $ArN_2^+ X^- \xrightarrow{Cu / HBr} ArBr + N_2 + CuX$       (Yield in Sandmeyer reaction is superior to Gattermann reaction).

  • Replacement by Iodide Ion:       $ArN_2^+ Cl^- + KI \rightarrow ArI + KCl + N_2$

  • Replacement by Fluoride Ion:       $ArN_2^+ Cl^- + HBF_4 \rightarrow ArN_2^+ BF_4^- \xrightarrow{\Delta} ArF + N_2 + BF_3$

  • Replacement by Hydrogen:       Reducing agents like hypophosphorous acid ($H_3PO_2$) or ethanol ($CH_3CH_2OH$) reduce diazonium salts to arenes:       $ArN_2^+ Cl^- + H_3PO_2 + H_2O \rightarrow ArH + N_2 + H_3PO_3 + HCl$       $ArN_2^+ Cl^- + CH_3CH_2OH \rightarrow ArH + N_2 + CH_3CHO + HCl$

  • Replacement by Hydroxyl Group:       Warming solution to $283\,K$ hydrolyses salt to phenol:       $ArN_2^+ Cl^- + H_2O \xrightarrow{283\,K} ArOH + N_2 + HCl$

  • Replacement by Nitro Group:       $ArN_2^+ Cl^- + HBF_4 \rightarrow ArN_2^+ BF_4^- \xrightarrow{NaNO_2 / Cu, \Delta} ArNO_2 + N_2 + NaBF_4$

  • B. Coupling Reactions (Retention of Diazo Group):

  • Reacts with phenol or aromatic amines to yield coloured azo compounds ($-N=N-$ linkage) used as dyes.

  • Coupling with Phenol:       $C_6H_5N_2^+ Cl^- + C_6H_5OH \xrightarrow{OH^-, pH\,9-10, 273-278\,K} p\text{-Hydroxyazobenzene (Orange dye)} + Cl^- + H_2O$

  • Coupling with Aniline:       $C_6H_5N_2^+ Cl^- + C_6H_5NH_2 \xrightarrow{H^+, pH\,4-5, 273-278\,K} p\text{-Aminoazobenzene (Yellow dye)} + HCl$

Solved Examples and Intext Questions

• Intext Question 13.1:

  • Classify the following amines as primary ($1^\circ$), secondary ($2^\circ$), or tertiary ($3^\circ$):

  • (i) Primary ($1^\circ$) amine

  • (ii) Tertiary ($3^\circ$) amine

  • (iii) Primary ($1^\circ$) amine

  • (iv) $(C_2H_5)_2CHNH_2$: Primary ($1^\circ$) amine

  • (v) $(C_2H_5)_2NH$: Secondary ($2^\circ$) amine

• Intext Question 13.2:

  • Write structures and IUPAC names of different isomeric amines having molecular formula C_4H_{11}N$.\n * **Primary (1^\circ) Amines**:\n * 1. CH_3CH_2CH_2CH_2NH_2: Butan-1-amine\n * 2. CH_3CH_2CH(NH_2)CH_3: Butan-2-amine\n * 3. (CH_3)_2CHCH_2NH_2: 2-Methylpropan-1-amine\n * 4. (CH_3)_3CNH_2: 2-Methylpropan-2-amine\n * **Secondary (2^\circ) Amines**:\n * 5. CH_3CH_2CH_2NHCH_3$:$N-Methylpropan-1-amine\n * 6. CH_3CH_2NHCH_2CH_3$:$N-Ethylethanamine\n * 7. (CH_3)_2CHNHCH_3$:$N-Methylpropan-2-amine\n * **Tertiary (3^\circ) Amine**:\n * 8. CH_3CH_2N(CH_3)_2$:$N,N-Dimethylethanamine\n * **Types of Isomerism Exhibited**:\n * **Chain Isomers**: 1 & 3; 2 & 4\n * **Position Isomers**: 1 & 2; 3 & 4\n * **Metamers**: 5, 6, 7, and 8\n\n* **Example 13.1**:\n * (i) Reaction of ethanolic NH_3$with$C_2H_5Cl:\n    NH_3 \xrightarrow{C_2H_5Cl} C_2H_5NH_2 \xrightarrow{C_2H_5Cl} (C_2H_5)_2NH \xrightarrow{C_2H_5Cl} (C_2H_5)_3N \xrightarrow{C_2H_5Cl} (C_2H_5)_4N^+ Cl^-\n * (ii) Ammonolysis of benzyl chloride and reaction of amine formed with two moles of CH_3Cl:\n    C_6H_5CH_2Cl \xrightarrow{NH_3} C_6H_5CH_2NH_2 \xrightarrow{2\,CH_3Cl} C_6H_5CH_2N(CH_3)_2$($N,N-Dimethylbenzylamine).\n\n* **Example 13.2**:\n * Conversions:\n * (i) CH_3CH_2Cl$to$CH_3CH_2CH_2NH_2:\n      CH_3CH_2Cl \xrightarrow{NaCN} CH_3CH_2CN \xrightarrow{LiAlH_4 \text{ or } H_2/Ni} CH_3CH_2CH_2NH_2\n * (ii) C_6H_5CH_2Cl$to$C_6H_5CH_2CH_2NH_2:\n      C_6H_5CH_2Cl \xrightarrow{NaCN} C_6H_5CH_2CN \xrightarrow{H_2/Ni} C_6H_5CH_2CH_2NH_2\n\n* **Example 13.3**:\n * (i) Structure and IUPAC name of amide giving propanamine by Hoffmann bromamide degradation:\n    Amide is Butanamide (CH_3CH_2CH_2CONH_2).\n * (ii) Amine produced by Hoffmann degradation of Benzamide:\n    Benzamide (C_6H_5CONH_2$) yields Aniline ($C_6H_5NH_2).\n\n* **Intext Question 13.3**:\n * Conversions:\n * (i) Benzene to Aniline:\n      \text{Benzene} \xrightarrow{HNO_3/H_2SO_4} \text{Nitrobenzene} \xrightarrow{Fe/HCl} \text{Aniline}\n * (ii) Benzene to N,N-dimethylaniline:\n      \text{Benzene} \xrightarrow{HNO_3/H_2SO_4} \text{Nitrobenzene} \xrightarrow{Fe/HCl} \text{Aniline} \xrightarrow{2\,CH_3Br} N,N\text{-Dimethylaniline}\n * (iii) Cl-(CH_2)_4-Cl to hexane-1,6-diamine:\n      Cl-(CH_2)_4-Cl \xrightarrow{2\,NaCN} NC-(CH_2)_4-CN \xrightarrow{H_2/Ni} H_2N-(CH_2)_6-NH_2\n\n* **Example 13.4**:\n * Arrange in decreasing order of basic strength: C_6H_5NH_2$,$C_2H_5NH_2$,$(C_2H_5)_2NH$,$NH_3:\n    (C_2H_5)_2NH > C_2H_5NH_2 > NH_3 > C_6H_5NH_2\n\n* **Intext Question 13.4**:\n * Increasing order of basic strength:\n * (i) C_6H_5NH_2 < NH_3 < C_6H_5CH_2NH_2 < C_2H_5NH_2 < (C_2H_5)_2NH\n * (ii) C_6H_5NH_2 < C_2H_5NH_2 < (C_2H_5)_3N < (C_2H_5)_2NH\n * (iii) C_6H_5NH_2 < C_6H_5CH_2NH_2 < (CH_3)_3N < CH_3NH_2 < (CH_3)_2NH\n\n* **Intext Question 13.5**:\n * Complete acid-base reactions:\n * (i) CH_3CH_2CH_2NH_2 + HCl \rightarrow CH_3CH_2CH_2NH_3^+ Cl^- (n-Propylammonium chloride)\n * (ii) (C_2H_5)_3N + HCl \rightarrow (C_2H_5)_3NH^+ Cl^- (Triethylammonium chloride)\n\n* **Intext Question 13.6**:\n * Reaction of final alkylation product of aniline with excess methyl iodide in presence of Na_2CO_3 solution:\n    C_6H_5NH_2 \xrightarrow{CH_3I} C_6H_5NHCH_3 \xrightarrow{CH_3I} C_6H_5N(CH_3)_2 \xrightarrow{CH_3I} C_6H_5N(CH_3)_3^+ I^-\n    2\,C_6H_5N(CH_3)_3^+ I^- + Na_2CO_3 \rightarrow [C_6H_5N(CH_3)_3^+]_2 CO_3^{2-} + 2\,NaI$($N,N,N-Trimethylanilinium carbonate).\n\n* **Intext Question 13.7**:\n * Reaction of aniline with benzoyl chloride:\n    C_6H_5NH_2 + C_6H_5COCl \xrightarrow{\text{Base}} C_6H_5NHCOC_6H_5 + HCl$($N-Phenylbenzamide).\n\n* **Intext Question 13.8**:\n * Isomers of C_3H_9N:\n 1. CH_3CH_2CH_2NH_2 (Propan-1-amine)\n 2. CH_3CH(NH_2)CH_3 (Propan-2-amine)\n 3. CH_3CH_2NHCH_3$($N-Methylethanamine)\n 4. (CH_3)_3N$($N,N-Dimethylmethanamine)\n * Isomers liberating N_2$gas with$HNO_2: Only primary amines: Propan-1-amine and Propan-2-amine.\n\n* **Example 13.5**:\n * Convert 4-Nitrotoluene to 2-bromobenzoic acid:\n 1. 4-Nitrotoluene + Br_2/Fe \rightarrow 3-Bromo-4-nitrotoluene.\n 2. Reduction with Sn/HCl \rightarrow 3-Bromo-4-methylaniline.\n 3. Diazotisation with NaNO_2/HCl (273-278\,K) \rightarrow 2-Bromo-4-methylbenzenediazonium chloride.\n 4. Reaction with H_3PO_2/H_2O \rightarrow 3-Bromotoluene.\n 5. Oxidation with KMnO_4/OH^- \rightarrow 2-Bromobenzoic acid.\n\n* **Intext Question 13.9**:\n * (i) Convert 3-Methylaniline to 3-Nitrotoluene:\n    3\text{-Methylaniline} \xrightarrow{NaNO_2/HCl, 273-278\,K} 3\text{-Methylbenzenediazonium chloride} \xrightarrow{HBF_4} 3\text{-Methylbenzenediazonium fluoroborate} \xrightarrow{NaNO_2/Cu, \Delta} 3\text{-Nitrotoluene}\n * (ii) Convert Aniline to 1,3,5-tribromobenzene:\n    \text{Aniline} \xrightarrow{Br_2 (aq)} \text{2,4,6-Tribromoaniline} \xrightarrow{NaNO_2/HCl, 273-278\,K} \text{2,4,6-Tribromobenzenediazonium chloride} \xrightarrow{H_3PO_2/H_2O} \text{1,3,5-Tribromobenzene}$$