A Level Chemistry OCR A - Module 4

Alicyclic

an aliphatic compound that is arranged in non-aromatic rings (with or without side chains).

Aliphatic

a compound containing carbon and hydrogen atoms joined in straight or branched chains or in non-aromatic rings.

Alkane

a homologous series with the general formula CnH2n+2.

Alkyl

a group with the general formula CnH2n+1.

Aromatic

an organic compound containing a benzene ring.

Curly Arrow

shows the movement of a pair of electrons. __must start from a bond, a lone pair of electrons or a negative charge.

Dipole

a partial charge on an atom which is caused by the differing electronegativities of atoms in a covalent bond.

Displayed Formula

the relative positions of atoms and the bonds between them.

Empirical Formula

the simplest whole number ratio of atoms of each element present in a compound.

Functional Group

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

General Formula

the simplest algebraic formula of a member of a homologous series.

Heterolytic Fission

when a covalent bond breaks, one bonding atom receives both electrons from the bonded pair.

Homologous Series

a series of organic compounds containing the same functional group with successive members differing by -CH2.

Homolytic Fission

when a covalent bond breaks, each bonding atom receives one electron from the bonding pair, forming 2 radicals.

IUPAC

International Union of Pure and Applied Chemistry.

Molecular Formula

the number and type of atoms of each element in a molecule.

Nomenclature

the naming system for compounds.

Organic Compound

a carbon-containing compound.

Radical

a species with an unpaired electron.

Reaction Mechanism

a series of steps that represent the overall reaction by showing the breaking and forming of bonds using curly arrows.

Saturated

an organic compound which only contains C-C single bonds.

Skeletal Formula

the simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving the carbon __and the functional groups.

Structural Formula

the minimal detail that shows the arrangement of atoms in a molecule.

Structural Isomers

compounds with the same molecular formula but different structural formulae.

Unsaturated

an organic compound which contains at least one C=C double bond, a C≡C triple bond or an aromatic ring.

σ-bond

a type of covalent bond which forms when atomic orbitals overlap head-on.

Boiling point

the temperature at which a liquid boils and becomes a gas.

Bond Enthalpy

the energy required to break one mole of gaseous bonds.

Complete Combustion

when a compound is burnt in a plentiful supply of oxygen.

Covalent Bond

a strong bond formed between 2 atoms due to the electrostatic attraction between a shared pair of electrons and the atomic nuclei.

Electron Pair Repulsion

pairs of electrons around a nucleus repel each other so the shape that a molecule adopts has these pairs of electrons positioned as far apart as possible.

Hydrocarbon

a compound which contains hydrogen and carbon atoms only.

Incomplete Combustion

when a compound is burnt in a limited supply of oxygen. When alkanes are __, water, carbon monoxide, particulates and some carbon dioxide may be produced/ solid carbon (soot)

Initiation

the first step in a radical substitution mechanism, involving the formation of the radicals.

London Forces

induced dipole-dipole interactions caused when the random movement of electrons creates a temporary dipole in one molecule which then induces a dipole in a neighbouring molecule.

Polar Bond

a covalent bond that has a permanent dipole due to the different electronegativities of the atoms that make up the bond
(the electronegativity difference is from 0-1.8)

Propagation

the intermediate steps in a radical substitution mechanism where a radical reacts with another species.

Radical

a species with an unpaired electron, E.g. Cl•.

Radical Substitution

a type of substitution reaction in which a radical replaces another atom/ group of atoms in a compound. Alkanes can undergo __ reactions with chlorine or bromine in the presence of UV light, forming a mixture of organic products (further substitution or reactions at different positions may occur).

Saturated

an organic compound which only contains single C-C bonds.

Termination

the final steps in a radical substitution mechanism in which 2 radicals react together to form a species which only contains paired electrons.

Tetrahedral

the shape of a molecule in which the central atom has 4 bonding pairs of electrons.

σ-bond

a type of covalent bond which forms when atomic orbitals overlap head-on. __ bonds can rotate freely.

π-bond

a type of covalent bond formed when adjacent p orbitals overlap sideways above and below the bonding C atoms.__ can't be rotated. As __have low bond enthalpy, alkenes are more reactive than alkanes.

Addition Polymerisation

the formation of a long chain molecule when many monomers join together (the polymer is the only product).

Addition Reaction

a reaction in which molecules combine to form a single product.

Alkene

an organic compound containing at least one C=C double bond, with the general formula CnH2n

Biodegradable

a substance that can be decomposed by bacteria or other living organisms.

Bond Enthalpy

the energy required to break one mole of gaseous bonds. Actual __ may differ from the average as the average __ considers a particular bond in a range of molecules.

Cahn-Ingold-Prelog (CIP) Priority Rules

a set of rules used to identify whether a stereoisomer is E or Z. Atoms with a higher atomic number have a higher priority. If the highest priority substituents on the same side of the double bond (both above or below), it's the Z isomer whereas if the highest priority groups are on the opposite sides (one above and one below), it's the E isomer.

Catalyst

a substance which increases the rate of a reaction without being used up.

Cis-Trans Isomerism

a type of E/Z isomerism in which the two substituent groups attached to the carbon atoms are the same. According to the CIP priority rules, cis isomers have the highest priority substituents on the same side of the double bond (both above or below) while trans isomers have them on the opposite sides (one above and one below).

Electron Pair Repulsion

pairs of electrons around a nucleus repel each other so the shape that a molecule adopts has these pairs of electrons positioned as far apart as possible. As a result, carbon atoms in alkenes have a trigonal planar shape and a bond angle of 120°.

Electrophile

an electron pair acceptor.

Electrophilic addition

a reaction in which a π bond is broken and 2 new σ bonds form as a result of the addition of an electron pair acceptor (electrophile).

E/Z Isomerism

a type of stereoisomerism caused by the restricted rotation of π bonds.

E/Z Isomerism

a type of stereoisomerism caused by the restricted rotation of π bonds. Two different groups must be attached to each carbon atom of the C=C group.

Z isomers

have the highest priority substituents on the same side of the double bond (both above or below).

E isomers

have the highest priority substituents on opposite sides of the double bond (one above and one below).

Heterolytic Fission

when a covalent bond breaks, one bonding atom receives both electrons from the bonding pair, resulting in the formation of oppositely charged ions.

Hydrocarbon

a compound which contains carbon and hydrogen atoms only.

Markownikoff's Rule

used to predict what the major product of an addition reaction will be when H-X is added to an unsymmetrical alkene. H attaches to the less substituted carbon to generate the more stable carbocation intermediate.

Monomer

a small molecule that is used to form polymers.

Photodegradable

a substance that can be broken down by light.

Polymer

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

Primary Carbocation

a molecule in which the carbon with the positive charge is only attached to one alkyl group. This is the least stable carbocation.

Repeat Unit

a structure within a polymer that appears over and over again. Joining many __ together would form the polymer.

Secondary Carbocation

a molecule in which the carbon with the positive charge is attached to two alkyl groups. This is more stable than a primary carbocation but less stable than a tertiary carbocation.

Stereoisomers

compounds with the same structural formula but a different arrangement of atoms in space.

Tertiary Carbocation

a molecule in which the carbon with the positive charge is attached to three alkyl groups. This is the most stable type of carbocation.

Trigonal Planar

the shape of a molecule in which the central atom has 3 bonding pairs of electrons.

Unsaturated

an organic compound containing at least one C=C double bond, a C≡C triple bond or an aromatic ring. The presence of a C=C double bond means that bromine water will be decolourised.

Alcohol

-an organic compound containing the OH functional group.
-polarity of the OH functional group means that __ can form hydrogen bonds and are soluble in water (when the alkyl chain is short).
-relatively low volatility compared with alkanes.

Aldehyde

an organic compound containing the -CHO functional group. __can be formed from the oxidation of primary alcohols using Cr O 2-/H+ and distillation.

Alkene

an organic compound containing a C=C double bond. __ can be formed from alcohols via the elimination of H2O using an acid catalyst and heat.

Carboxylic Acid

an organic compound containing the -COOH functional group. __can be formed from the oxidation of primary alcohols using Cr O 2-/H+ and reflux.

Combustion

a rapid exothermic reaction of a substance with oxygen.

Elimination

a type of reaction in which 2 atoms/groups of atoms are removed from a molecule.

Haloalkanes

an organic compound containing a halogen atom (F/Cl/Br/I) bound to an alkyl chain. Haloalkanes can be formed from alcohols via a substitution reaction with halide ions in the presence of acid.

Ketone

an organic compound containing the C=O functional group in the middle of an alkyl chain. __ can be formed by the oxidation of a secondary alcohol.

Oxidation

the loss of electrons/increase in oxidation number. Alcohols can be __ using Cr O 2-/H+.

Oxidising Agent

a substance that can oxidise another species while being reduced.

Polar Bond

a covalent bond in which there is an unequal share of the electrons between the 2 atoms due to the differing electronegativities of the atoms involved. One atom will have a partial positive charge while the other will have a partial negative charge.

Primary Alcohol

an alcohol in which the OH is attached to a __ carbon atom (i.e. RCH2OH).

Primary Alcohol

An alcohol that can be oxidised to form either an aldehyde or a carboxylic acid, depending on the conditions.

Secondary Alcohol

An alcohol in which the OH is attached to a __carbon atom (i.e. R CHOH). __ can be oxidised under reflux with Cr O 2-/H+ to form a ketone.

Tertiary Alcohol

An alcohol in which the OH is attached to a tertiary carbon atom (i.e. R3COH). __alcohols cannot be oxidised.

Bond Enthalpy

The energy required to break one mole of gaseous bonds. The __ of the carbon halogen bond in haloalkanes decreases from C-F to C-I.

CFC

A class of compound made up of carbon, fluorine and chlorine, used as refrigerants and aerosol propellants. __ can be broken down by UV light in the upper atmosphere to form chlorine radicals which catalyse the breakdown of ozone.

Haloalkane

An organic compound containing a halogen atom (F/ Cl/ Br/ I) bound to an alkyl chain.

Hydrolysis

The breakdown of a compound as a result of a reaction with water. The rate of haloalkane __ for different carbon-halogen bonds can be determined via a reaction with water in the presence of AgNO3 and ethanol.

Nucleophile

An electron pair donor.

Nucleophilic Substitution

A reaction in which an electron pair donor attacks an electrophilic atom (an atom with a partial or full positive charge) to replace an atom / group of atoms.

Ozone

A molecule with the formula O3, which absorbs UV light in the atmosphere. The breakdown of __ can be catalysed by chlorine radicals as well as other radicals such as NO.

Radical

A species with an unpaired electron (e.g. •Cl).

Substitution

A reaction in which one atom/ group of atoms replaces another. Haloalkanes can undergo __ reactions with aqueous alkali or with water. The rate of reaction increases from C-F to C-I due to the decreasing bond enthalpy of the carbon-halogen bond.

Anhydrous Salt

A salt such as MgSO4 or CaCl2 which is used to remove traces of water from an organic solution.

Distillation

A technique in which a liquid is heated then the vapour is cooled and collected in a separate flask to the reaction mixture. During __, the condenser must be positioned horizontally.

Quickfit Apparatus

Glassware that easily fits together in a variety of arrangements.

Redistillation

A technique used to purify an organic liquid using multiple distillations.