PYQ Vault

MHT-CET Chemistry · Formula sheet

Aldehydes, Ketones and Carboxylic Acids formulas

11 formulas, 1 reference table and 12 common traps for MHT-CET Chemistry Aldehydes, Ketones and Carboxylic Acids, grouped by subtopic.

Full notes with worked examples

Nomenclature and Classification of Aldehydes, Ketones and Carboxylic Acids

Learn this subtopic in the notes

General Formula, Simple Ketones, and the Physical Facts

General formulas

aldehyde / ketone: CnH2nO;acid: CnH2nO2\text{aldehyde / ketone: } \text{C}_n\text{H}_{2n}\text{O};\qquad \text{acid: } \text{C}_n\text{H}_{2n}\text{O}_2

IUPAC Priority: COOH Beats CHO Beats OH

Priority and prefixes

COOH (parent)→CHO as ’formyl’;CHO (parent)→OH as ’hydroxy’;C=O (parent)→OH as ’hydroxy’\text{COOH (parent)} \to \text{CHO as 'formyl'};\quad \text{CHO (parent)} \to \text{OH as 'hydroxy'};\quad \text{C=O (parent)} \to \text{OH as 'hydroxy'}

The Named Acids: Mono-, Di- and Tricarboxylic

Common nameIUPAC nameCOOH groups
Formic / acetic / propionicMethanoic / ethanoic / propanoic1
Butyric / valeric / caproicButanoic / pentanoic / hexanoic1
Valeric and caproic are MONO — the planted 'dicarboxylic' options.
Oxalic / malonic / succinicEthanedioic / propanedioic / butanedioic2
Glutaric / adipicPentanedioic / hexanedioic2
PhthalicBenzene-1,2-dicarboxylic2
The one aromatic acid on the list that is NOT mono.
Citric2-Hydroxypropane-1,2,3-tricarboxylic3
The only tricarboxylic acid asked.
Benzoic / salicylic / o-toluicBenzoic / 2-hydroxybenzoic / 2-methylbenzoic1
C1–C6 mono: F-A-P-B-V-C; C2–C6 di: O-M-S-G-A.

Common traps

Hearing 'valeric' and 'glutaric' as the same kind of name

The -ic ending says nothing about the count. Valeric (C5) and caproic (C6) are straight-chain MONOacids; glutaric (C5) and adipic (C6) are the DIacids of the same length.

Calling acetophenone a simple ketone

Phenyl and methyl are different groups — acetophenone is mixed. The simple one on the list is always benzophenone.

Naming the compound as a phenol because the OH is on the ring

Ring OH is a phenol only when nothing outranks it. With CHO or COOH present the OH is a hydroxy prefix; 'formyl-phenol' and 'carboxy-phenol' names are the planted options.

Preparation of Aldehydes and Ketones

Learn this subtopic in the notes

Rosenmund, Stephen and DIBAL-H: Three Ways to an Aldehyde

Three aldehyde routes

RCOCl→H2/Pd-BaSO4RCHO;RCN→SnCl2/HCl; H3O+RCHO;RCN→DIBAL-H; H3O+RCHO\text{RCOCl} \xrightarrow{\text{H}_2/\text{Pd-BaSO}_4} \text{RCHO};\quad \text{RCN} \xrightarrow{\text{SnCl}_2/\text{HCl};\ \text{H}_3\text{O}^+} \text{RCHO};\quad \text{RCN} \xrightarrow{\text{DIBAL-H};\ \text{H}_3\text{O}^+} \text{RCHO}

Grignard and Dialkylcadmium: Ketones and Alcohols

Cadmium route to ketones

R2Cd+2 R’COCl→2 R’COR+CdCl2\text{R}_2\text{Cd} + 2\,\text{R'COCl} \to 2\,\text{R'COR} + \text{CdCl}_2

Etard Reaction and Hydrolysis Routes

Etard reaction

C6H5CH3→CrO2Cl2/CS2Etard complex→H3O+C6H5CHO\text{C}_6\text{H}_5\text{CH}_3 \xrightarrow{\text{CrO}_2\text{Cl}_2/\text{CS}_2} \text{Etard complex} \xrightarrow{\text{H}_3\text{O}^+} \text{C}_6\text{H}_5\text{CHO}

Common traps

Assigning DIBAL-H to Rosenmund

DIBAL-H reduces NITRILES and esters; Rosenmund is hydrogen over poisoned palladium on an ACID CHLORIDE. Both give aldehydes, and the paper lists both reagents in one question.

Stopping at dimethylcadmium

Dimethylcadmium is A, the intermediate. The question asks for B, after acetyl chloride — propanone. 'Dimethyl cadmium' is option (a) every time.

Reading the Etard intermediate as benzal chloride

Chromyl chloride does not chlorinate the side chain; A is a chromium complex. The paper offers benzal chloride as option (a) for A's product; the answer to 'B' is benzaldehyde either way.

Nucleophilic Addition and Condensation Reactions

Learn this subtopic in the notes

Cyanohydrins, Hemiacetals and the Ammonia Derivatives

Addition then loss of water

>C=O+H2N-Z→>C(OH)-NH-Z→−H2O>C=N-Z\text{>C=O} + \text{H}_2\text{N-Z} \to \text{>C(OH)-NH-Z} \xrightarrow{-\text{H}_2\text{O}} \text{>C=N-Z}

Aldol Reaction and the Cannizzaro Reaction

Aldol and Cannizzaro

2 RCH2CHO→OH−RCH2CH(OH)CHR-CHO→ΔRCH2CH=CR-CHO;2 ArCHO→conc. OH−ArCOO−+ArCH2OH2\,\text{RCH}_2\text{CHO} \xrightarrow{\text{OH}^-} \text{RCH}_2\text{CH(OH)CHR-CHO} \xrightarrow{\Delta} \text{RCH}_2\text{CH=CR-CHO};\qquad 2\,\text{ArCHO} \xrightarrow{\text{conc. OH}^-} \text{ArCOO}^- + \text{ArCH}_2\text{OH}

Common traps

Confusing hydrazine with semicarbazide

NH₂NH₂ gives a hydrazone; the semicarbazone needs the urea-like NH₂NHCONH₂. All four ammonia derivatives are offered together; match the Z group to the product name.

Reducing the wrong aldehyde in the crossed Cannizzaro

Methanal is the stronger hydride donor, so IT is oxidised (to methanoic acid) and benzaldehyde is reduced (to benzyl alcohol). 'Methanol and benzoic acid' is the reversed, planted option.

Oxidation, Reduction and Identification Tests

Learn this subtopic in the notes

Clemmensen, Wolff–Kishner and Hydride Reductions

C=O to CH₂

Clemmensen: Zn-Hg / conc. HCl;Wolff–Kishner: NH2NH2 then KOH / ethylene glycol\text{Clemmensen: Zn-Hg / conc. HCl};\qquad \text{Wolff–Kishner: NH}_2\text{NH}_2 \text{ then KOH / ethylene glycol}

Tollens, Fehling, Schiff and the Haloform Test

Tollens' reaction

RCHO+2[Ag(NH3)2]++3OH−→RCOO−+2Ag↓+4NH3+2H2O\text{RCHO} + 2[\text{Ag(NH}_3)_2]^+ + 3\text{OH}^- \to \text{RCOO}^- + 2\text{Ag}\downarrow + 4\text{NH}_3 + 2\text{H}_2\text{O}

Common traps

Losing a carbon in Wolff–Kishner

The reduction replaces O by two H and changes nothing else. Propiophenone (three side-chain carbons) gives n-PROPYLbenzene; 'ethylbenzene' is the planted option.

Expecting the haloform reaction from every carbonyl

It is a test for the CH₃CO– fragment, not for carbonyls in general. Ethanal passes; propanal, one carbon longer on the wrong side, fails.

Carboxylic Acids: Properties, Reactions and Derivatives

Learn this subtopic in the notes

Boiling Points of Acids, and Making Them

Grignard to acid

R-MgX→(i) CO2 (dry ice); (ii) H3O+R-COOH(one carbon more than R)\text{R-MgX} \xrightarrow{\text{(i) CO}_2\text{ (dry ice); (ii) H}_3\text{O}^+} \text{R-COOH} \quad (\text{one carbon more than R})

Acid Chlorides, Anhydrides, Esters and Amides

Derivative ↔ acid

RCOOH→PCl5RCOCl→H2ORCOOH;RCOOR’→NaOHRCOONa→HClRCOOH\text{RCOOH} \xrightarrow{\text{PCl}_5} \text{RCOCl} \xrightarrow{\text{H}_2\text{O}} \text{RCOOH};\qquad \text{RCOOR'} \xrightarrow{\text{NaOH}} \text{RCOONa} \xrightarrow{\text{HCl}} \text{RCOOH}

Common traps

Forgetting the carbon that CO₂ brings

Ethyl-MgBr does not give ethanoic acid. The CO₂ carbon becomes the COOH: ethyl → propanoic acid, isopropyl → 2-methylpropanoic acid.

Stopping at the sodium salt

Base hydrolysis of an ester gives the carboxylate; the question then adds concentrated HCl, which protonates it. The answer is the ACID, not sodium propanoate — offered as option (a).

More MHT-CET Chemistry formula sheets