Nitrobenzene (–NO2) can be reduced to aniline (–NH2) by various reducing systems: Sn/HCl, Zn/NH4Cl (or Zn/HCl), and other metal/acid reductions. Hence all listed reagents reduce nitrobenzene to aniline.
Gabriel phthalimide synthesis requires an alkyl halide (R–X) for N-alkylation. Chlorobenzene is an aryl halide and does not undergo nucleophilic substitution to give aniline. The other methods (Hofmann degradation of benzamide, reduction of nitrobenzene by LiAlH4 or Sn/HCl) do give aniline.
Hofmann bromamide (Hofmann degradation) requires a primary amide (RCONH2). N-substituted amides (secondary amides) such as CH3CONHCH3 do not undergo the Hofmann bromamide reaction to give an amine.
Acetamide (CH3CONH2) treated with Br2 and KOH undergoes Hofmann degradation to give methylamine (CH3NH2), not acetic acid. Also bromine does not merely catalyse hydrolysis; the reaction is a bromine‑mediated rearrangement (Hofmann degradation). Therefore both assertion and reason are false.
Sequence: CH3CH2Br + NaOH (aq) → CH3CH2OH (ethanol). Oxidation (KMnO4/H+) → CH3COOH (acetic acid). Conversion to amide (CH3CONH2) by NH3, then Hofmann degradation (Br2/KOH) removes C=O carbon to give CH3NH2 (methylamine, methanamine). So D is methanamine (CH3NH2).
Nitrous acid reacts with primary nitroalkanes (red solution) and secondary nitroalkanes (blue solution) but tertiary nitroalkanes do not give these characteristic reactions with HNO2 (they lack the necessary reactivity).
Acylation of amines with acid chlorides in the presence of aqueous base (e.g. aniline + benzoyl chloride → acylated product) is the Schotten–Baumann reaction.
Aldehyde + primary amine → imine (Schiff's base, RCH=NR'). The imine formation is a condensation (loss of water).
Secondary amines react with nitrous acid to give N-nitroso derivatives (R2N–NO), not diazonium salts of the form R2N–N= NCl. The written product in (b) is incorrect. (Tertiary amines are inert to diazotization; primary aromatic amines give diazonium salts.)
Acetic anhydride acetylates the amino group of aniline forming the amide acetanilide (C6H5NHCOCH3). This protects the –NH2 and prevents electrophilic substitution on the ring until deprotection.
Answer: b. In aqueous solution: dimethylamine > methylamine > trimethylamine > ammonia. Solvation and steric hindrance reduce the basicity of tertiary amines in water.
Replacement of an aryl diazonium group by chloride (Ar–N2+ → Ar–Cl) is achieved by the Sandmeyer reaction using CuCl (copper(I) chloride).
Answer: a. Nitrobenzene reduced by Fe/HCl → aniline (C6H5NH2). Diazotisation and hydrolysis of the diazonium salt gives phenol (C6H5OH).
The nitro group is a strong deactivator and meta-director. Further nitration of nitrobenzene gives mainly the meta isomer, i.e. 1,3-dinitrobenzene.
Answer: b. Primary amines RNH2 treated with HNO2 yield alcohols (ROH). For the product to be optically active the alcohol must be at a chiral centre; pentan-2-amine gives pentan-2-ol, which is chiral.
Characteristic tests: primary nitroalkanes with HNO2 give a red solution, secondary give a blue solution, tertiary do not react (no colour).
Acetylation requires an N–H bond. Tertiary amines (e.g. triethylamine) have no N–H and therefore do not form amides (they cannot be acetylated). Primary and secondary amines undergo acetylation.
Alkyl groups are electron donating and increase the basicity of aniline by increasing electron density on nitrogen. Electron-withdrawing halogens (especially nitro) decrease basicity. Thus 2,4-dimethylaniline (electron-donating substituents) is the most basic among the choices.
Answer: a. Reduction of an alkyl nitrite cleaves the O–N bond to give the alcohol (ethanol) and reduces the nitroso fragment to hydroxylamine; the latter is obtained as its hydrochloride (NH2OH·HCl).
The correct systematic name for a pentan-3-amine with two methyl groups on nitrogen is N,N-dimethyl-3-methylpentan-3-amine (writing as N,N-dimethyl-3-methylpentan-3-amine). This names the dimethyl substitution on N and the methyl substituent at C‑3 of the pentane chain.
An ester RCOOCH3 treated with excess CH3MgBr undergoes two nucleophilic additions at the carbonyl carbon: the ester is first converted to a ketone (by expulsion of OCH3− as MgBrOCH3) and then the ketone reacts with a second equivalent of CH3− to give after aqueous workup a tertiary (here secondary if R = H) alkoxide which on hydrolysis gives the corresponding alcohol. Thus the product is the alcohol (structure shown in option a).
Heating the ammonium salt of benzoic acid with P2O5 effects dehydration of the ammonium carboxylate to give benzonitrile (C6H5–C≡N). Reduction of benzonitrile (e.g. by catalytic hydrogenation or LiAlH4) gives benzylamine (C6H5–CH2NH2). Treatment of a primary aliphatic/aromatic‑substituted primary amine with NaNO2/HCl at 0–5 °C converts it into the corresponding diazonium which, for benzylic (aliphatic) amines, rapidly decomposes to give the alcohol. Hence the final product is benzyl alcohol (C6H5–CH2OH).
Primary amines react with chloroform and base (KOH) in the carbylamine reaction to give the corresponding isocyanide (R–NC) (this is Y). Acidic hydrolysis of an isocyanide (R–NC) in the presence of acid/formic acid gives the corresponding primary amine as its ammonium salt (R–NH3+ Cl−). Thus X is the ammonium chloride of the original alkyl group (for a methyl example, CH3NH3+Cl−, written as CH3NHCl in the option list).
Electrophilic aromatic substitution (EAS) is typified by halogenation of an activated aromatic ring using a Lewis acid such as AlCl3 to generate the electrophile (Cl+). The stepwise mechanism involves attack of the aromatic π system on the electrophile to give a σ‑complex, followed by deprotonation to restore aromaticity. Thus the chlorination using Cl2/AlCl3 is an electrophilic substitution.
Answer: b. Oxalic acid with ammonia on strong heating gives the diamide oxamide (NH2–CO–CO–NH2) by replacement of both –OH groups by –NH2 (dehydrative amidation).
C3H7NO2 corresponds to two important amino acid isomers: the α‑amino acid (alanine) where the NH2 is on C‑2, and the β‑amino acid (β‑alanine) where NH2 is on the terminal carbon next to the carboxyl (C‑3). (Other functional isomers with the same formula are possible in principle, but these two are the usual textbook examples.)
Isomers of C3H7NO2 (common constitutional isomers — amino acids): 1) 2‑Aminopropanoic acid (alanine) — CH3–CH(NH2)–COOH. 2) 3‑Aminopropanoic acid (β‑alanine) — NH2–CH2–CH2–COOH.
Use qualitative tests — ninhydrin (detects –NH2 of amino acids), reaction with nitrous acid (deamination of primary amine), solubility and salt formation; nitroethane gives typical nitro‑compound chemistry (alpha‑bromination, negative ninhydrin).
Two constitutional isomers of C2H5NO2 are nitroethane (CH3CH2NO2) and aminoacetic acid (glycine, NH2CH2COOH). Distinguishing tests: (1) Ninhydrin test: glycine (an amino acid) gives a purple colour with ninhydrin, nitroethane does not. (2) Reaction with NaNO2/HCl (nitrous acid): the primary amine in glycine reacts (deamination) whereas nitroethane (a nitro compound) is inert to nitrous acid under these conditions. (3) Acid–base behaviour: glycine shows zwitterionic behaviour and forms salts with base/acid; nitroethane does not behave as an amino acid.
Short textbook answers: ii) Nitrobenzene → Aniline on electrolytic reduction (strongly acidic). i), iii), iv) depend on conditions; i) nitroalkane under strong acid may hydrolyse/rearrange (can give corresponding carbonyl compound), iii) KMnO4 oxidises primary amines to carboxylic acids or leads to oxidative cleavage, iv) peracid oxidation of oximes can give nitrile oxides or lead to amide formation (Beckmann‑type rearrangement products). (Specific isolated products depend on exact reagents and conditions.)
i) Acidic treatment of nitroalkanes leads to nitronic acid tautomers and under strong acid conditions rearrangements/hydrolysis can occur — 2‑nitropropane when strongly acidified may undergo dehydration/hydrolysis to give acetone and nitrous products. ii) Electrolytic reduction of nitrobenzene in strongly acidic medium gives aniline (reduction through phenylhydroxylamine to aniline). iii) Strong oxidation of a primary aliphatic amine (tert‑butylamine is primary) with KMnO4 leads to oxidative cleavage/deamination to give the corresponding carboxylic acid fragments or oxidised products; tert‑butylamine is oxidised to tert‑butylamine oxidation products (eventual cleavage to acetic/CO2 products) — practically one obtains oxidation to tert‑butyl nitro or further to CO2 and N2 species. iv) Oxidation of an oxime with a peracid typically gives an amide via the Beckmann‑type or gives nitrile oxides depending on conditions; acetone oxime oxidised with peracid can give acetamide (after rearrangement) or cleavage products; peracid oxidation commonly converts oximes to nitro compounds or nitrile oxides depending on reagent and conditions.
Use standard stepwise transformations: nitration for polynitration; reduction and diazotisation for conversion to phenols; controlled partial reductions produce azoxy‑ and hydrazo‑ and hydroxylamine derivatives; full reduction gives aniline.
Brief conversions: i) Nitrobenzene → (strong nitration: HNO3/H2SO4, repeated nitration) → 1,3,5‑trinitrobenzene (use very vigorous nitration conditions). ii) Nitrobenzene → nitration gives mainly m‑nitro products; to get o‑/p‑nitrophenol: first reduce to phenol or convert via diazonium route: nitrobenzene → (reduction to aniline → diazotisation → hydrolysis) gives phenol (o/p mixture upon directing substituents). Alternatively, nisoldipine? Practically: reduce nitrobenzene to aniline (Fe/HCl), acetylate, then nitration to give p‑ and o‑nitroacetanilide; hydrolysis yields o‑ and p‑nitroaniline; convert aniline derivatives to phenols by diazotisation (NaNO2/HCl, 0–5 °C) then warm water to give o/p‑nitrophenol. iii) m‑Nitroaniline: nitration of nitrobenzene gives m‑dinitrobenzene then reduction of one nitro to amine gives m‑nitroaniline; or protect/convert groups appropriately. iv) Azoxybenzene: partial reduction of nitrobenzene (e.g. by Zn/alkali or catalytic partial reduction) gives azoxybenzene. v) Hydrazobenzene: reduction of azoxybenzene (cleavage of N=O) or reduction of nitrobenzene under controlled conditions (e.g. Na in ethanol) yields hydrazobenzene. vi) N‑Phenylhydroxylamine: partial reduction of nitrobenzene (e.g. using Zn/HCl at low temperature) gives N‑phenylhydroxylamine; controlled electrolytic reduction also gives it. vii) Aniline: exhaustive reduction of nitrobenzene (Fe/HCl, Sn/HCl or catalytic hydrogenation) gives aniline.
The sequences are standard transformations: nitrobenzene → aniline → diazonium → phenol; aryl diazonium → substitution (CN, Cl, OH, etc.); alkyl halide → nitrile → hydrolysis → amide/acid; methylamine → acylation → acetamide → reduction → secondary amine; aniline → acetanilide → nitration → hydrolysis → nitroaniline. (If you provide a clearer typed scheme I will name each A/B/C exactly.)
Because the printed multi‑part scheme is heavily corrupted by OCR, I list the common textbook transformations and the likely intermediates: i) C6H5NO2 --(Fe/HCl)→ C6H5NH2 (A). C6H5NH2 + HNO2 (0–5 °C) → C6H5N2+ (B, diazonium). C6H5N2+ + H2O → C6H5OH (C). ii) C6H5N2+Cl− --(CuCN)→ C6H5CN (A). C6H5CN + H2O/H+ (hydrolysis) → C6H5COOH (B). C6H5COOH + NH3 (or reduction) → C6H5CH2NH2 (variants). iii) CH3CH2I + NaCN → CH3CH2CN (A). Hydrolysis (partial) gives CH3CH2CONH2 (B) or CH3CH2COOH (C) depending on hydrolysis. iv) CH3NH2 --(CH3COCl)→ CH3NHCOCH3 (acetamide derivative A). Reduction (B2H6) gives CH3NHCH3 (secondary amine C). v) C6H5NH2 --((CH3CO)2O, pyridine)→ acetanilide (A). Nitration (HNO3/H2SO4) gives p‑nitroacetanilide (B). Hydrolysis (H2O/H+) yields p‑nitroaniline (C). vi) N2Cl (diazonium chloride) → via pH manipulations gives various substitution products; e.g. N2Cl → Ar–OH at pH 4–5. vii) CH3CH2NC --(HgO, H2O)→ CH3CH2CONH2 (amide) → hydrolysis yields CH3CH2COOH. (Overall identification: A, B, C are standard nitration/diazotisation/hydrolysis intermdiates: aniline, diazonium salt, phenol/other substitution products.)
Each entry is a standard named reaction/test; the above gives the definition and typical utility. (If you want mechanisms or example equations for any one, I can expand it.)
Concise notes: i) Hofmann bromamide (Hofmann) degradation: Conversion of amide (RCONH2) to primary amine (RNH2) with loss of one carbon using Br2 and NaOH (or CH3NO2)? (Actually Hofmann bromamide uses Br2/NaOH to give amine with one fewer carbon). ii) Ammonolysis: nucleophilic substitution where ammonia replaces a leaving group (e.g., RX + NH3 → RNH2). iii) Gabriel synthesis: preparation of primary amines by alkylation of phthalimide followed by hydrolysis or hydrazinolysis to give RNH2 (selective for primary amines). iv) Schotten–Baumann reaction: formation of amides by reaction of amines with acid chlorides under basic aqueous conditions (often pyridine) to neutralize HCl. v) Carbylamine (isocyanide) reaction: primary amines react with chloroform and base (KOH) to give isocyanides (R–NC); a test for primary amines. vi) Mustard oil reaction (olefin formation?): 'mustard oil' usually refers to allyl isothiocyanate produced by hydrolysis of sinigrin; in organic reactions 'mustard oils' are formed from glucosinolates. vii) Coupling reaction: diazonium salts couple with activated aromatic rings (e.g. phenols, arylamines) to give azo dyes (Ar–N=N–Ar'). viii) Diazotisation: conversion of primary aromatic amines to diazonium salts using NaNO2/HCl at 0–5 °C; diazonium salts are versatile intermediates. ix) Gomberg reaction: generation of triphenylmethyl radical and related radical chemistry (Gomberg discovered trityl radical).
Hinsberg reagent test is the classical textbook method; nitrous acid behaviour and NMR complement it.
Distinguishing tests: (1) Hinsberg test: Treat amine with Hinsberg reagent (benzenesulfonyl chloride) and aqueous NaOH. Primary amines give soluble sulfonamide salts (after base) → on acidification give sulfonamide precipitate; secondary amines give insoluble N‑alkyl sulfonamides (do not dissolve in base); tertiary amines do not react and remain unchanged. (2) Nitroprusside or copper reagents and reaction with nitrous acid: primary aliphatic amines react with nitrous acid to give unstable aliphatic diazonium which decomposes with N2 evolution (observe gas/alkoxide formation); secondary amines give N‑nitrosamines (yellow oil) with NaNO2/HCl; tertiary amines give no diazonium (may give decomposition products). (3) Spectroscopic methods (IR, NMR): N–H signals (two for primary, one for secondary, none for tertiary) in 1H NMR are diagnostic.
Concise resonance, electronic and mechanistic rationales provided for each point.
Short accounts: i) Aniline is strongly deactivated toward Friedel–Crafts because the –NH2 coordinates to Lewis acids (AlCl3), forming anilinium salt or complex; this removes the lone pair from resonance donation, preventing the electrophilic substitution and often destroying the catalyst. ii) Aromatic diazonium salts (Ar–N2+) are stabilized by resonance with the aromatic ring; aliphatic diazonium ions lack such resonance and readily decompose, so they are unstable. iii) pKb: aniline is less basic (higher pKb) than methylamine because the lone pair on N in aniline is delocalized into the benzene ring (resonance), reducing availability for protonation; in methylamine the lone pair is fully available and is electron‑donated by the methyl group (+I), increasing basicity. iv) Gabriel synthesis gives primary amines selectively because the phthalimide anion undergoes alkylation at nitrogen (SN2) and after hydrolysis liberates a primary amine without over‑alkylation (no formation of secondary/tertiary amines). v) Ethylamine is small and can hydrogen‑bond with water to give a soluble salt; aniline is less soluble because the aromatic ring is hydrophobic and the N‑lone pair is involved in resonance, reducing hydrogen bonding and solubility. vi) Amines are more basic than amides because in amides the lone pair on nitrogen is delocalized into the carbonyl (resonance), greatly reducing its availability to accept a proton; in amines the lone pair is localized and more basic. vii) In nitration of aniline under strongly acidic conditions the –NH2 is protonated (to –NH3+), which is a strong meta‑director; moreover to prevent oxidation and protonation aniline is often first acetylated to acetanilide before nitration. Hence direct nitration of aniline gives appreciable m‑product due to protonation under acidic nitrating conditions.
These orderings depend on solvent and steric/inductive/resonance effects; the classical aqueous‑phase orders: electron‑donating alkyl groups increase basicity but steric/solvation can reverse tertiary vs secondary in water; electron‑withdrawing substituents (NO2, Cl) decrease basicity; aromatic amines are less basic due to resonance. (If you want a cleaned, stepwise list for each subpart with justification I can provide it.)
All three routes use reduction of a –CN, –CONH2 or –NO2 functional group to give the primary amine: (CN → CH2NH2), (CONH2 → CH2NH2), (NO2 → NH2) using LiAlH4 or catalytic hydrogenation (or suitable reductants).
Preparations: i) CH3CH2CH2CN (butanenitrile) —(reduction, e.g. LiAlH4 or catalytic hydrogenation)→ CH3CH2CH2CH2NH2 (but this gives butylamine). To obtain propan‑1‑amine (CH3CH2CH2NH2) start from propionitrile (CH3CH2CN) and reduce: CH3CH2CN + 4 [H] → CH3CH2CH2NH2 (use LiAlH4 or H2/Pd). ii) Propanamide (CH3CH2CONH2) on reduction (e.g. LiAlH4) → propan‑1‑amine. iii) 1‑Nitropropane (CH3CH2CH2NO2) on catalytic hydrogenation (H2/Pd) or using metal/HCl reduction → propan‑1‑amine (via reduction of nitro to amino).
If you provide the exact typed reaction scheme I will name A, B, C exactly. The usual transformations: nitro → amine (LiAlH4), then alkylation (alkyl halide) to give higher amines, then acid treatment gives salts, etc.
Given the scheme is unclear from OCR, a typical sequence: reduction of a nitroalkane (CH3NO2) with LiAlH4 gives methylamine (CH3NH2) (A). Alkylation with CH2CH2Br (or alkyl halide) gives N‑ethylmethylamine (secondary amine) (B). Acid work‑up or further reactions give tertiary amine (C).
Standard transformations: acylation for amide formation; nitrosation of secondary amines with nitrous acid gives N‑nitrosamines.
i) Diethylamine (Et2NH) + acetyl chloride (CH3COCl) or acetic anhydride → N,N‑diethylacetamide (Et2N–COCH3) via acylation (Schotten–Baumann conditions or pyridine). ii) N‑nitrosation: Diethylamine treated with NaNO2/HCl at 0–5 °C (or with nitrosyl chloride) gives N‑nitrosodiethylamine (Et2N–NO).
If the intended sequence was conversion of a dicarboxylic acid derivative to an amine via acid chloride → amide → reduction, then A = acid chloride, B = amide, C = diamine. Please supply the exact starting formula for precise IDs.
Typical transformation: a diol (R–CH2–OH) converted with SOCl2 gives the corresponding di‑chloride or alkyl chloride (R–CH2–Cl) (A). Treatment with NH3 converts alkyl chloride to primary amine (R–CH2–NH2) (B). Reduction with LiAlH4 of an intermediate (e.g. amide formed earlier) would give the amine (C).
The condensation of a primary amine with an aldehyde gives an imine (Schiff base) with loss of water: PhNH2 + PhCHO → PhCH= NPh (N‑benzylideneaniline).
Aniline (PhNH2) reacts with benzaldehyde (PhCHO) to give an imine (Schiff base): N‑benzylideneaniline (Ph–CH=N–Ph) (A).
Mechanism: nucleophilic addition of –NH2 to carbonyl → carbinolamine → loss of water → imine; optional subsequent reduction gives amine (reductive amination).
A carbonyl compound (aldehyde/ketone) reacts with a primary amine (CH2–NH2) under acid catalysis to give an imine (Schiff base), R–CH=N–CH2 (after dehydration). Subsequent reduction (e.g. NaBH4) gives the corresponding secondary amine, R–CH2–NH–CH2–. So the immediate product under trace H+ is the imine (R–CH=NH–CH2…), and after reduction the secondary amine.
The text of the reaction as given is too garbled to reconstruct the starting structure and the sequence of reagents unambiguously. To solve such problems I need the correct structural formula(s) and reagent order. Please supply a clear image or the fully typed reaction sequence; then I will (concise) identify A, B, C and D with stepwise reasoning (showing nitrile/amidation/hydrolysis/Hofmann/Curtius etc. as appropriate).
Cannot reliably identify A–D from the provided (OCR-corrupted) scheme. Please upload a clear image or re-type the structures/reaction sequence.
Stepwise reasoning: - Geminal dibromides R–CHBr2 react with KCN to give the geminal dicyano compound R–CH(CN)2. Hydrolysis of the dinitrile gives the geminal dicarboxylic acid R–CH(COOH)2 which on heating (decarboxylation of the malonic-type acid) yields the monocarboxylic acid R–COOH (loss of CO2). - To obtain D with molar mass 74 (propanoic acid, C3H6O2), work backwards: D = propanoic acid (C3). The amine C that gives D on diazotisation + oxidation must be propylamine (C3). By Hofmann rearrangement (Br2 / KOH) an amide R–CO–NH2 is converted to R–NH2 (same R); hence the amide came from the acid B by reaction with NH3. - Therefore B must be butanoic acid (CH3CH2CH2COOH). Heating B with liquid NH3 gives butanamide (CH3CH2CH2CONH2); Hofmann (Br2/KOH) converts it to propylamine (CH3CH2CH2NH2) because loss of the carbonyl carbon occurs in the rearrangement. - Diazotisation of propylamine (NaNO2/HCl, 0 °C) gives an unstable aliphatic diazonium which on oxidation is converted to propanoic acid (D), M = 74. - The original dibromo A must be the geminal dibromide that leads (after CN substitution and hydrolysis/decarboxylation) to butanoic acid; that is 1,1-dibromobutane (CH3CH2CH2CHBr2).
A = 1,1-dibromobutane; B = butanoic acid (butyric acid), CH3CH2CH2COOH; C = propylamine, CH3CH2CH2NH2; D = propanoic acid (propionic acid), CH3CH2COOH.
Stepwise identification: - Friedel–Crafts alkylation: benzene + CH3Cl/AlCl3 → toluene (A). - Nitration: toluene (activating, ortho/para director) nitration gives mainly p-nitrotoluene (B) as major isomer. - Reduction: Sn/HCl reduces the nitro group to amino → p-toluidine (C). - Diazotisation: NaNO2/HCl (0–5 °C) converts the amino group to the arenediazonium salt (D, p-CH3C6H4–N2+). - Sandmeyer-type substitution: CuCN replaces the diazonium with CN → p-cyanotoluene (E). - Hydrolysis/oxidation of the –CN group (strong oxidative conditions, e.g. KMnO4/heat) converts –CN → –COOH; the major isolated product is p-methylbenzoic acid (p-toluic acid). (Where regioselectivity noted: para is major product throughout because of steric/electronic effects.)
A = toluene (C6H5CH3); B = p-nitrotoluene (major) (p-CH3C6H4NO2); C = p-toluidine (p-CH3C6H4NH2); D = p-toluenediazonium salt (p-CH3C6H4–N2+); E = p-cyanotoluene (p-CH3C6H4CN). Major product after hydrolysis/oxidation of the nitrile = p-methylbenzoic acid (p-toluic acid, p-CH3C6H4COOH).