Aldehydes, Ketones, Carboxylic Acids, Amines, and Biomolecules

Comprehensive practice vocabulary flashcards covering the nomenclature, structures, preparations, reactions, mechanisms, and biological functions of aldehydes, ketones, carboxylic acids, amines, diazonium salts, carbohydrates, proteins, and nucleic acids.

Carbonyl Group

A functional group consisting of a carbon-oxygen double bond ($>C=O$), where the carbonyl carbon is $sp^2$-hybridised and forms three planar $\sigma$-bonds and one $\pi$-bond with oxygen.

Orbital Diagram of Carbonyl Group

A structural model showing the $sp^2$-hybridised carbonyl carbon forming a $\sigma$-bond with oxygen, a parallel unhybridised $p$-orbital overlap forming a $\pi$-bond above and below the coplanar trigonal framework, two non-bonding electron pairs on oxygen, and bond angles of approximately $120^\circ$.

Rosenmund Reduction

The catalytic hydrogenation of an acyl chloride (acid chloride) over palladium supported on barium sulphate ($Pd-BaSO_4$) to yield the corresponding aldehyde.

Stephen Reaction

The reduction of a nitrile to an intermediate imine using stannous chloride ($SnCl_2$) in the presence of hydrochloric acid ($HCl$), followed by acid hydrolysis to produce an aldehyde.

Etard Reaction

The selective oxidation of toluene or a substituted methylbenzene with chromyl chloride ($CrO_2Cl_2$) in carbon disulfide ($CS_2$) to form a brown chromium complex, which yields benzaldehyde upon hydrolysis.

Gatterman-Koch Reaction

The industrial electrophilic formylation of benzene or a substituted benzene with carbon monoxide ($CO$) and hydrogen chloride ($HCl$) in the presence of anhydrous aluminium chloride ($AlCl_3$) or cuprous chloride ($CuCl$) to produce benzaldehyde.

Cyanohydrin

An organic compound containing a cyano ($-CN$) group and a hydroxyl ($-OH$) group on the same carbon atom, prepared by the base-catalyzed nucleophilic addition of hydrogen cyanide ($HCN$) to an aldehyde or ketone.

Hemiacetal

An alkoxyalcohol intermediate formed by the addition of one equivalent of a monohydric alcohol to the carbonyl group of an aldehyde in the presence of dry hydrogen chloride gas.

Acetal

A gem-dialkoxy compound formed when a hemiacetal reacts with a second equivalent of alcohol in the presence of dry hydrogen chloride gas.

Schiff's Base

A substituted imine containing a $>C=NR$ functional group, prepared by the acid-catalyzed nucleophilic addition of a primary amine to an aldehyde or ketone followed by rapid dehydration.

Clemmensen Reduction

The chemical reduction of the carbonyl group of an aldehyde or ketone to a methylene ($-CH_2-$) group by heating with zinc amalgam ($Zn-Hg$) and concentrated hydrochloric acid ($HCl$).

Wolff-Kishner Reduction

The conversion of the carbonyl group of an aldehyde or ketone into a methylene ($-CH_2-$) group by treatment with hydrazine ($NH_2NH_2$) followed by heating with potassium hydroxide ($KOH$) or sodium hydroxide in ethylene glycol.

Tollens' Test

A diagnostic chemical test in which an aldehyde reduces ammoniacal silver nitrate solution (Tollens' reagent) in alkaline medium to precipitate a bright silver mirror, while the aldehyde is oxidised to a carboxylate anion.

Fehling's Test

A chemical test distinguishing aliphatic aldehydes from aromatic aldehydes and ketones using an alkaline solution of copper sulphate and sodium potassium tartarate (Rochelle salt), which yields a red-brown precipitate of cuprous oxide upon heating.

Haloform Reaction

The base-promoted oxidative cleavage of methyl ketones or secondary alcohols having a $CH_3CH(OH)-$ group using sodium hypohalite ($NaOX$) to yield a haloform ($CHX_3$) and a carboxylate salt with one fewer carbon atom.

Aldol Condensation

A reaction in which aldehydes or ketones with at least one $\alpha$-hydrogen condense in the presence of dilute alkali to yield $\beta$-hydroxy aldehydes or $\beta$-hydroxy ketones, which subsequently eliminate water to form $\alpha,\beta$-unsaturated carbonyl compounds.

Cannizzaro Reaction

A base-catalyzed disproportionation reaction undergone by aldehydes lacking an $\alpha$-hydrogen atom upon heating with concentrated alkali, resulting in simultaneous reduction of one molecule to an alcohol and oxidation of another to a carboxylic acid salt.

Hell-Volhard-Zelinsky (HVZ) Reaction

The selective halogenation of a carboxylic acid containing an $\alpha$-hydrogen at the $\alpha$-position by treatment with chlorine or bromine in the presence of a catalytic amount of red phosphorus, yielding an $\alpha$-halocarboxylic acid.

Primary Amine

A derivative of ammonia formed by replacing one hydrogen atom with an alkyl or aryl group, having the general formula $R-NH_2$ or $Ar-NH_2$.

Geometry of Trimethylamine

A pyramidal arrangement resulting from an $sp^3$-hybridised nitrogen carrying three methyl groups and one unshared electron pair, where lone-pair–bond-pair repulsions compress the $C-N-C$ bond angle to $108^\circ$.

Ammonolysis

The nucleophilic cleavage of the carbon-halogen ($C-X$) bond of an alkyl or benzyl halide by an ethanolic solution of ammonia in a sealed tube at $373\,K$, yielding a mixture of primary, secondary, and tertiary amines alongside quaternary ammonium salts.

Gabriel Phthalimide Synthesis

A synthetic method for preparing pure aliphatic primary amines by reacting phthalimide with ethanolic potassium hydroxide, followed by alkylation of potassium phthalimide with an alkyl halide and subsequent alkaline hydrolysis.

Hoffmann Bromamide Degradation Reaction

A reaction for preparing primary amines by treating an amide with bromine in an aqueous or ethanolic solution of sodium hydroxide, resulting in an amine product containing one carbon atom fewer than the starting amide.

Carbylamine Reaction

A diagnostic test for primary aliphatic and aromatic amines, in which heating with chloroform and ethanolic potassium hydroxide produces foul-smelling isocyanides (carbylamines).

Hinsberg's Reagent

Benzenesulphonyl chloride ($C_6H_5SO_2Cl$), a reagent used to distinguish and separate primary, secondary, and tertiary amines based on the acidity and alkali-solubility of their sulphonamide derivatives.

Diazotisation

The chemical conversion of a primary aromatic amine into a diazonium salt by reaction with nitrous acid ($NaNO_2 + HCl$) at low temperatures ($273\text{--}278\,K$).

Sandmeyer Reaction

The nucleophilic displacement of the diazonium group in an arenediazonium salt by $-Cl$, $-Br$, or $-CN$ using cuprous chloride, cuprous bromide, or cuprous cyanide, respectively.

Coupling Reaction

An electrophilic aromatic substitution reaction between an arenediazonium ion and an electron-rich aromatic substrate (such as phenol or aniline) to produce brightly colored azo dyes joined by an $-N=N-$ linkage.

Carbohydrate

An optically active polyhydroxy aldehyde or ketone, or a substance that yields such units upon hydrolysis.

Reducing Sugar

Any carbohydrate containing a free or potential aldehyde or ketone group (such as all monosaccharides, maltose, and lactose) capable of reducing Fehling's solution and Tollens' reagent.

Glycosidic Linkage

The covalent ether-like oxide linkage joining two monosaccharide units together through an oxygen atom, formed via the condensation of their hydroxyl groups with the loss of a water molecule.

Invert Sugar

The equimolar mixture of $D\text{-(+)--glucose}$ and $D\text{-(-)--fructose}$ obtained by acid or enzymatic hydrolysis of dextrorotatory sucrose, resulting in a net laevorotatory solution because the laevorotation of fructose ($-92.4^\circ$) outweighs the dextrorotation of glucose ($+52.5^\circ$).

Anomers

Cyclic hemiacetal or hemiketal stereoisomers of monosaccharides (such as $\alpha\text{-D--glucopyranose}$ and $\beta\text{-D--glucopyranose}$) that differ in configuration specifically at the carbonyl carbon atom ($C1$ in aldoses or $C2$ in ketoses).

Amylose

The water-soluble component of starch ($15\text{--}20\%$) consisting of an unbranched polymer of $200\text{--}1000$ $\alpha\text{-D-(+)--glucose}$ units joined exclusively by $C1\text{--}C4$ glycosidic linkages.

Amylopectin

The water-insoluble component of starch ($80\text{--}85\%$) composed of a branched-chain polymer of $\alpha\text{-D--glucose}$ units linked by $C1\text{--}C4$ glycosidic bonds with branching occurring through $C1\text{--}C6$ glycosidic linkages.

Zwitter Ion

A dipolar, overall electrically neutral ion formed in aqueous solution when the carboxyl group ($-COOH$) of an amino acid loses a proton to the basic amino group ($-NH_2$), resulting in $-COO^-$ and $-NH_3^+$ within the same molecule.

Essential Amino Acid

An amino acid that cannot be synthesized by the human body and must be supplied through the diet (e.g., valine, leucine, and lysine).

Peptide Linkage

An amide bond ($-CO-NH-$) formed between the carboxyl group of one $\alpha$-amino acid and the amino group of another, accompanied by the elimination of a water molecule.

Denaturation of Protein

The disruption of secondary and tertiary structures of a native protein caused by physical changes (such as heat) or chemical changes (such as $pH$ shifts), resulting in loss of biological activity while leaving the primary structure intact.

Nucleoside

A biomolecular unit formed by the covalent attachment of a nitrogenous purine or pyrimidine base to the $1'$ position of a pentose sugar (ribose or 2-deoxyribose).

Nucleotide

A phosphate ester of a nucleoside, produced when a phosphoric acid moiety is esterified at the $5'$ position of the pentose sugar.

Phosphodiester Linkage

The phosphate ester bond connecting the $5'$ carbon of one nucleotide's pentose sugar to the $3'$ carbon of an adjacent nucleotide's sugar, forming the backbone of nucleic acids.