CBSE Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids

High-yield vocabulary flashcards on Aldehydes, Ketones, and Carboxylic Acids covering key name reactions, tests, reagents, mechanisms, and acid-base concepts from CBSE Class 12 NCERT Chemistry.

Rosenmund reduction

The catalytic hydrogenation of an acyl chloride ($RCOCl$) with hydrogen gas over palladium on barium sulphate ($Pd/BaSO_4$) to produce an aldehyde: $RCOCl + H_2 \rightarrow RCHO + HCl$.

Stephen reaction

The reduction of a nitrile ($RCN$) with tin(II) chloride and hydrochloric acid ($SnCl_2/HCl$) to form an imine intermediate ($RCH=NH$), followed by hydrolysis to yield an aldehyde ($RCHO$).

DIBAL-H reduction

The selective reduction of nitriles ($RCN$) or esters ($RCOOR'$) with diisobutylaluminium hydride, followed by hydrolysis, to yield aldehydes ($RCHO$).

Etard reaction

The mild oxidation of toluene ($C_6H_5CH_3$) with chromyl chloride ($CrO_2Cl_2$) to form a chromium complex, which gives benzaldehyde ($C_6H_5CHO$) upon hydrolysis.

Gattermann-Koch reaction

The conversion of benzene ($C_6H_6$) to benzaldehyde ($C_6H_5CHO$) by treatment with carbon monoxide and hydrogen chloride ($CO/HCl$) in the presence of anhydrous $AlCl_3/CuCl$.

Friedel-Crafts acylation of benzene

The electrophilic substitution reaction of benzene ($C_6H_6$) with acetyl chloride ($CH_3COCl$) in the presence of anhydrous aluminium chloride ($AlCl_3$) to form acetophenone ($C_6H_5COCH_3$) and $HCl$.

Clemmensen reduction

The reduction of the carbonyl group of aldehydes or ketones ($RCOR'$) into a methylene group ($-CH_2-$) using zinc amalgam and concentrated hydrochloric acid ($Zn(Hg)/\text{concentrated } HCl$): $RCOR' + 4[H] \rightarrow RCH_2R' + H_2O$.

Wolff-Kishner reduction

The deoxygenation of an aldehyde or ketone ($RCOR'$) to a hydrocarbon ($RCH_2R'$) via reaction with hydrazine ($NH_2NH_2$), followed by heating with potassium hydroxide ($KOH$) in ethylene glycol: $RCOR' + NH_2NH_2 \rightarrow RCH_2R' + N_2 + H_2O$.

Aldol condensation

The base-catalyzed (e.g., dilute $NaOH$) reaction of carbonyl compounds containing $\alpha$-hydrogens (such as ethanal) to form a $\beta$-hydroxyaldehyde (3-hydroxybutanal), which upon heating undergoes dehydration to give an $\alpha,\beta$-unsaturated aldehyde (but-2-enal).

Cross aldol condensation

An aldol reaction between two different carbonyl compounds (such as ethanal and propanal); when both contain $\alpha$-hydrogens, each can act as a nucleophile or an electrophile, yielding a mixture of four products (two self-condensation and two cross-condensation products).

Cannizzaro reaction

A base-mediated disproportionation (redox) reaction of aldehydes lacking $\alpha$-hydrogens (such as benzaldehyde) upon heating with concentrated $NaOH$, producing an alcohol and a carboxylate salt: $2C_6H_5CHO + NaOH \rightarrow C_6H_5CH_2OH + C_6H_5COONa$.

Hell-Volhard-Zelinsky (HVZ) reaction

The halogenation of carboxylic acids bearing an $\alpha$-hydrogen with bromine in the presence of red phosphorus ($Br_2/\text{red phosphorus}$) to produce an $\alpha$-bromo acid: $RCH_2COOH + Br_2 \rightarrow RCHBrCOOH + HBr$.

Kolbe electrolysis

The electrolytic decarboxylation of an aqueous sodium carboxylate solution, causing alkyl radicals to couple into symmetrical alkanes: $2RCOONa + 2H_2O \rightarrow R-R + 2CO_2 + H_2 + 2NaOH$.

Tollens' reagent

An ammoniacal silver nitrate solution ($[Ag(NH_3)_2]^+$) that oxidizes aldehydes (such as propanal) to carboxylate anions while forming a diagnostic metallic silver mirror, but does not react with ketones (such as propanone): $RCHO + 2[Ag(NH_3)_2]^+ + 3OH^- \rightarrow RCOO^- + 2Ag + 4NH_3 + 2H_2O$.

Fehling's reagent

An alkaline copper complex solution that distinguishes aliphatic aldehydes (like ethanal, which upon heating reduces $Cu^{2+}$ to give a reddish-brown $Cu_2O$ precipitate: $RCHO + 2Cu^{2+} + 5OH^- \rightarrow RCOO^- + Cu_2O + 3H_2O$) from aromatic aldehydes (such as benzaldehyde, which does not react).

Iodoform test

A chemical test using iodine in base ($I_2/NaOH$) to identify methyl carbonyl ($CH_3CO-$) or methyl carbinol ($CH_3CH(OH)-$) groups, giving a characteristic yellow precipitate of iodoform ($CHI_3$).

2,4-DNP reagent

2,4-Dinitrophenylhydrazine, a reagent that reacts with aldehydes and ketones in weak acid to form brightly colored (yellow, orange, or red) 2,4-dinitrophenylhydrazone derivatives: $>C=O + H_2NNHC_6H_3(NO_2)_2 \rightarrow >C=NNHC_6H_3(NO_2)_2 + H_2O$.

Sodium bicarbonate ($NaHCO_3$) test

A functional group test used to distinguish carboxylic acids from phenols and esters; carboxylic acids (such as benzoic acid) decompose sodium bicarbonate to release effervescence of carbon dioxide gas: $C_6H_5COOH + NaHCO_3 \rightarrow C_6H_5COONa + CO_2 + H_2O$.

Cyanohydrin

An organic compound containing a cyano and a hydroxyl group on the same carbon atom ($RCH(OH)CN$), synthesized via base-catalyzed addition of $HCN$ to a carbonyl compound to generate the reactive $CN^-$ nucleophile.

Oxime

A compound containing the $>C=N-OH$ group, synthesized by the condensation of an aldehyde or ketone with hydroxylamine ($NH_2OH$) under weakly acidic conditions.

Semicarbazone

A crystalline condensation product containing the $>C=NNHCONH_2$ group, prepared by reacting an aldehyde or ketone with semicarbazide ($NH_2NHCONH_2$) in weak acid.

Acetal

A gem-diether compound ($CH_3CH(OC_2H_5)_2$) formed by the addition of two equivalents of an alcohol (such as ethanol) to an aldehyde (such as ethanal) in dry $HCl$, which can be reverted to the carbonyl compound by aqueous acid hydrolysis.

Electrophilicity of aldehydes vs. ketones

The increased chemical reactivity of aldehydes relative to ketones toward nucleophilic addition due to lower steric hindrance and fewer electron-donating alkyl groups attached to the carbonyl carbon.

Aromatic resonance deactivation of benzaldehyde

The reduced electrophilicity and reactivity of benzaldehyde toward nucleophiles compared to aliphatic aldehydes (like propanal), caused by electron delocalization from the attached benzene ring into the carbonyl carbon.

$\alpha$-Hydrogen acidity in carbonyls

The acidic property of hydrogen atoms attached to the carbon adjacent to a carbonyl group, resulting from the strong electron-withdrawing nature of the $>C=O$ moiety and resonance delocalization of the conjugate enolate anion.

Carboxylate ion resonance stabilization

The symmetrical resonance delocalization of negative charge across two equivalent, highly electronegative oxygen atoms in carboxylate ions, making carboxylic acids significantly more acidic than phenols (where phenoxide delocalizes charge onto less electronegative carbon atoms).

Substituent effects on carboxylic acidity

The phenomenon wherein electron-withdrawing groups stabilize the negative carboxylate anion to enhance acid strength (e.g., $ClCH_2COOH > CH_3COOH$), whereas electron-donating groups destabilize it and decrease acid strength.

Thionyl chloride ($SOCl_2$) chlorination

The preferred method for preparing acyl chlorides from carboxylic acids ($RCOOH + SOCl_2 \rightarrow RCOCl + SO_2 + HCl$) because the gaseous by-products ($SO_2$ and $HCl$) escape readily, facilitating reaction workup and purification.

Diborane selectivity in carboxylic acid reduction

The chemoselective reduction of carboxylic acids to primary alcohols ($RCOOH + 4[H] \rightarrow RCH_2OH + H_2O$) using diborane, which does not easily reduce functional groups such as esters, nitro, or halo groups (unlike $NaBH_4$, which cannot reduce $-COOH$ at all).

Fischer esterification equilibrium

The reversible, acid-catalyzed condensation of a carboxylic acid with an alcohol ($RCOOH + R'OH \rightleftharpoons RCOOR' + H_2O$), which is driven to high yields by continuously removing either water or the ester product.

Soda lime decarboxylation

The elimination of a carbon atom from a sodium carboxylate ($RCOONa$) by heating with soda lime ($NaOH/CaO$) to produce an alkane with one fewer carbon: $RCOONa + NaOH \rightarrow RH + Na_2CO_3$.

Friedel-Crafts inertness of benzoic acid

The failure of benzoic acid to undergo Friedel-Crafts reactions because the strongly electron-withdrawing carboxylic acid group ($-COOH$) deactivates the aromatic ring and complexes directly with the anhydrous $AlCl_3$ Lewis acid catalyst.