Definitions 3: Module 6: Organic Chemistry & Analysis Chemistry OCR A A Level

2,4-dinitrophenylhydrazine

Also known as Brady’s reagent, this compound forms an orange precipitate in the presence of aldehydes and ketones. The melting point of the 2,4-DNP derivative of a carbonyl can be used to identify the carbonyl compound.

Elemental Analysis

A sample is analysed to determine the proportion of elements that make up the compound present. This is done by converting a known amount of an unknown sample into simple known compounds.

Amide Hydrolysis

Amides can either be hydrolysed under acidic conditions (forming carboxylic acids and ammonium salts) or under alkaline conditions (forming carboxylate salts and either ammonia or an amine). Polyamides can be hydrolysed in a similar way.

Stationary Phase

A substance through which the mobile phase moves in chromatography. This is typically a solid although a solid coated in a liquid may be used in GC.

Carbon-13 NMR Spectroscopy

A type of NMR spectroscopy which analyses 13C nuclei.

The number of peaks in the spectrum shows the number of different environments and the chemical shifts show what environments are present.

Chiral Centre

A carbon atom which is bonded to 4 different groups.

Alkylation

A reaction which is used to form substituted aromatic compounds, using a haloalkane to form a C-C bond in the presence of a halogen carrier.

α-Amino Acid

A compound with the general formula RCH(NH2)COOH, where an amino group and a carboxylic acid group are bonded to the same carbon atom. The carboxylic acid group of an amino acid reacts with alkalis or can be used to form esters. The amine group of an amino acid reacts with acids.

Bronsted-Lowry Acid

A proton donor.

Primary Amide

An organic compound which contains the functional group RNH2 (where R is an alkyl chain).

Ester Hydrolysis

Esters can either be hydrolysed with hot aqueous acid (forming carboxylic acids and alcohols) or with hot aqueous alkali (forming carboxylate salts and alcohols). Polyesters can be hydrolysed in a similar way.

Recrystallisation

A technique used to purify an organic solid. The sample is dissolved in the minimum volume of hot solvent and filtered. The filtrate is then cooled before being filtered under reduced pressure. The purified solid will collect on the filter paper in the Büchner funnel.

Polymer

A large molecule made from many small units that have been bonded together.

Electrophilic Substitution

A reaction in which an electrophile (an electron pair acceptor) reacts with another compound to replace an atom / group of atoms.

Acylation

A reaction that is used to form substituted aromatic compounds, using an acyl chloride to form a C-C bond in the presence of a halogen carrier.

Secondary Amide

An organic compound which contains the functional group R2NH (where R is an alkyl chain).

Kekulé's Structure of Benzene

A model of benzene which contains alternating C=C double and C-C single bonds in a hexagonal ring, with each carbon atom bound to one hydrogen atom.

Esterification

The process of making esters. Esters can be made by a reaction between carboxylic acids and alcohols in the presence of an acid catalyst or by a reaction between acid anhydrides and alcohols.

Oxidation

The loss of electrons/ increase in oxidation number.

Aldehyde

An organic compound containing the C=O functional group at the end of an alkyl chain. Aldehydes form a silver mirror when reacted with Tollens’ reagent. Aldehydes can be oxidised to carboxylic acids with acidified potassium dichromate, causing a colour change from orange to green.

Aromatic Compound

A compound containing at least one benzene ring.

Functional Group

A group of atoms responsible for the characteristic reactions of a compound.

Condensation Polymerisation

A long chain molecule formed when monomers react together with the release of small molecules such as water. Types of condensation polymers are polyamides (formed from carboxylic acids / acyl chlorides and amines) and polyesters (formed from carboxylic acids/ acyl chlorides and alcohols).

Benzene

Benzene is a colourless, sweet smelling, flammable liquid.