Term
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Definition
| The equilibrium transfer of a proton from an acid to a base |
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Term
| Acid dissociation constant (Ka) |
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Definition
The equilibrium constant for the dissociation of a weak acid in water:
Ka = (H+)(A-)/(HA) |
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Term
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Definition
| A buffer that maintains a pH value below 7 |
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Term
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Definition
| The minimum energy required for a reaction to occur |
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Term
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Definition
| A functional group RC=O derived from a carboxylic acid |
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Term
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Definition
| The introduction of an acyl group into an organic molecule |
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Term
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Definition
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Term
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Definition
| A polymer obtained by the addition of monomers to the end of a growing chain (alkenes) |
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Term
| Adsorption Chromatography |
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Definition
| Involves a solid phase of finely-divided particles as the fixed (stationary) phase and a liquid or gas as the moving (mobile) phase |
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Term
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Definition
| The name commonly used for compounds having a primary amino group attached to the carbon atom adjacent to a carboxylic acid group |
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Term
| Analytical chromatography |
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Definition
| Operates with small amounts of material and aims to identify and measure the relative proportions of the various components present in a mixture |
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Term
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Definition
| Monocyclic or polycyclic aromatic hydrocarbons, such as benzene |
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Term
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Definition
| The name traditionally used in relation to benzene and its derivatives |
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Term
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Definition
| A carbon atom with four different atoms or groups attached that is devoid of symmetry |
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Term
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Definition
| The largest peak in a mass spectrum |
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Term
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Definition
| A buffer that maintains a pH value above 7 |
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Term
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Definition
| A second-order step in a reaction mechanism |
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Term
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Definition
| Capable of being broken down by micro-organisms (enzymes) |
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Term
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Definition
| A renewable, non-petroleum-based fuel obtained by transesterification from vegetable oils, such as soya bean and rapeseed oil |
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Term
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Definition
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Term
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Definition
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Term
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Definition
| The pH range over which a weak acid/base can show buffer action |
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Term
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Definition
| The concentration range over which a weak acid/base can show buffer action |
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Term
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Definition
| A solution that resists change in pH on addition of small amounts of acid or base, or on dilution |
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Term
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Definition
| An eluent gas, such as helium, used as the moving phase in gas-liquid chromatography |
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Term
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Definition
| A substance that alters the rate a of reaction without itself being consumed |
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Term
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Definition
| Addition polymer. A polymer obtained by the addition of monomers to the end of a growing chain (alkenes) |
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Term
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Definition
| Structural isomers which occur when there is more than one way of arranging the carbon skeleton of a molecule |
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Term
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Definition
| In NMR, the amount (measures in parts per million, ppm) by which a H-1 or a C-13 resonance is shifted from that of the internal standard |
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Term
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Definition
| Drugs possessing chiral centres, often single-enantiomer structures |
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Term
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Definition
| A molecule that cannot be superimposed on its mirror image |
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Term
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Definition
| A separated pattern of substances in a mixture, obtained by chromatography |
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Term
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Definition
| An apparatus used for chromatographic separation of volatile components in a mixture |
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Term
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Definition
| A technique for separating the components of a mixture on the basis of their different affinities for a stationary and a moving phase |
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Term
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Definition
| Involves a stationary phase of finely-divided alumina or silica gel in a vertical glass tube and an organic solvent as the moving phase |
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Term
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Definition
| A polymer involving the loss of small molecules, obtained by the reaction between molecules having two functional groups |
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Term
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Definition
| The increase in stability associated with electron delocalisation |
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Term
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Definition
| Electrons that are spread over more than one atom in a molecule, eg as in benzene where 6 delocalised electrons lie above and below the plane of the hexagonal ring |
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Term
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Definition
| In NMR, a nucleus is said to be deshielded when the electron density surrounding it is reduced, giving rise to a downfield shift (larger δ value) |
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Term
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Definition
| A base that forms two moles of hydroxide ions per mole of base, eg Ba(OH)2 |
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Term
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Definition
| The conversion of ArNH2 into ArN2+ |
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Term
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Definition
| An acid that forms two moles of protons per mole of acid, eg H2SO4 |
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Term
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Definition
| In NMR, a peak that is split into 2 parts |
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Term
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Definition
| A fully biodegradable aliphatic-aromatic co-polyester, used for disposable packaging, based on butane-1,4-diol and benzene-1,4-dicarboxylic acid |
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Term
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Definition
| An electron-seeking species, eg a positive ion or the more positive end of a polar molecule, which usually accepts a pair of electrons |
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Term
| Electrophilic substitution reaction |
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Definition
| Mechanistically, an electrophilic addition-elimination reaction resulting in overall substitution, typically involving arenes, eg Nitration of Benzene |
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Term
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Definition
| The solution emerging from a chromatographic column |
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Term
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Definition
| The solvent used as the moving phase in column chromatography |
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Term
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Definition
| The process of washing the components of a mixture down a chromatographic column |
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Term
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Definition
| Three-dimensional, non-superimposable molecular structure mirror images |
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Term
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Definition
| A change in which heat energy is taken in |
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Term
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Definition
| The point during a titration when the colour of an indicator lies half-way between the acid and base colours |
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Term
| Equilibrium constant (Kc) |
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Definition
The ratio of concentrations of products and reactants raised to the powers of their stoichiometric coefficients;
3A ⇋ 2B + C
Kc = [B]2[C]/[A]3 |
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Term
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Definition
| The point on a titation curve at which stoichiometrically equivalent amounts of acid and base have been mixed together |
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Term
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Definition
| A change in which heat energy is given out |
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Term
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Definition
| Also known as geometrical or cis-trans isomerism |
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Term
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Definition
| Arise due to restricted rotation about carbon-carbon double bonds when the two pairs of attached substituents can be arranged in 2 different ways |
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Term
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Definition
| Contain long chains of polypeptides which occur in bundles, eg Keratin |
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Term
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Definition
| In mass spectrometry, the breakdown of a molecular ion into smaller, positively-charged ions and radicals |
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Term
| Free-radical substitution reaction |
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Definition
| A reaction in which the hydrogen atom of a C-H bone is replaced by a halogen atom; a chain-reaction mechanism involves attack on a neutral molecule by a radical (halogen atom) |
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Term
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Definition
| An electrophilic substitution reaction, involving an acylium cation, resulting in carbon-carbon bond formation |
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Term
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Definition
| An atom or group of atoms which, when present in different molecules, results in similar chemical properties |
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Term
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Definition
| Structural isomers which contain different functional groups |
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Term
| Gas-liquid chromatography |
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Definition
| Involves an inert powder coated with a film of a non-volatile liquid, packed in a tube (the stationary phase) and a carrier gas (the moving phase) |
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Term
| Glass-transition temperature |
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Definition
| The temperature at which a polymer changes from a hard and glass-like state to a more flexible and mouldable state |
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Term
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Definition
| Contains long chains of amino acids, soluble in water, which are folded into roughly spherical shapes, eg haemoglobin |
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Term
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Definition
| A stable species which is liberated during an organic chemical reaction |
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Term
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Definition
| When exactly one-half of the equivalence volume of a base or acid has been added to an acid or base |
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Term
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Definition
| A system with the species present in different phases |
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Term
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Definition
| Molecules composed of more than one type of element, eg HCl |
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Term
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Definition
| A system with all species present in the same phase |
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Term
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Definition
| A family of organic molecules which all contain the same functional group but have an increasing number of carbon atoms; each member can be represented by a general formula |
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Term
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Definition
| Diatomic molecules composed of only one type of element, eg Cl2 |
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Term
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Definition
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Term
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Definition
| Waste-treatment technology involving the combustion of organic materials |
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Term
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Definition
| Usually a weak organic acid with strongly coloured acid and base forms |
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Term
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Definition
| The rate of change of concentration at the start of a reaction |
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Term
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Definition
| In NMR, a computer-generated line, sumperimposed on the spectrum, which measures the relative areas under the various peaks in the spectrum |
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Term
| Ionic product of water (Kw) |
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Definition
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Term
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Definition
| The pH at which an amino acid has no net charge |
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Term
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Definition
| Molecules with the same chemical formula but in which the atoms are arranged differently |
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Term
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Definition
| A sheet-like polyamide, used in bullet-proof vests, derived from benzene-1,4-dicarboxylic acid and benzene-1,4-diamine |
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Term
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Definition
| An area of land on which rubbish is dumped |
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Term
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Definition
| States that a system at equilibrium will respond to oppose any changes imposed upon it |
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Term
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Definition
| A measure of the torque exerted on a magnetic system, eg a bar magnet, when placed in a magnetic field |
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Term
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Definition
| Moving phase; in chromatography, the liquid or gaseous phase that passes through a fixed stationary phase. |
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Term
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Definition
| The species formed in a mass spectrometer by the loss of one electron from a molecule |
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Term
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Definition
| A base that forms one mole of hydroxide ions per molecule of base, eg NaOH |
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Term
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Definition
| An acid that forms one mole of protons per mole of acid, eg HCl |
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Term
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Definition
| Mobile phase; in chromatography, the liquid or gaseous phase that passes through a fixed stationary phase. |
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Term
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Definition
| In NMR, a peak that is split into many parts |
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Term
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Definition
| In NMR, signals for protons adjacent to n equivalent neighbours are split into n+1 peaks |
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Term
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Definition
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Term
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Definition
| The 1,3-linked ismoer of Kevlar, used in flame-resistant clothing |
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Term
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Definition
| A property that influences the behaviour of certain nuclei, typically H-1 and C-13, in a magnetic field; nuclei posessing even numbersof both protons and neutrons, such as C-12 and O-16 lack magnetic properties and do not give rise to NMR signals |
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Term
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Definition
| An electron-rich molecule or ion able to donate a pair of electrons |
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Term
| Nucleophilic addition reaction |
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Definition
| A reaction in which an electron-rich molecule or ion (with a lone pair of electrons) attacks the electron-deficient atom of a polar group, eg addition of HCN to an aldehyde or ketone |
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Term
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Definition
| Stereoisomers (enantiomers) which rotate the plane of plane-polarised light equally but in opposite directions |
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Term
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Definition
| Capable of rotating the plane of plane-polarised light |
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Term
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Definition
| The sum of the powers of the concentration terms in the rate equation |
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Term
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Definition
| Involves a thin layer of water adsorbed onto chromatographic paper (the stationary phase) and a solvent or solvent mixture (the moving phase) |
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Term
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Definition
| Molecular ion; The species formed in a mass spectrometer by the loss of one electron from a molecule |
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Term
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Definition
| Involves a thin, non-volatile liquid film helf on the surface of an inert solid or within the fibres of a supportng matrix (the stationary phase) and a liquid or gas (the moving phase) |
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Term
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Definition
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Term
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Definition
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Term
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Definition
| At half equivalence, pH = pKa for a weak acid |
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Term
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Definition
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Term
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Definition
| A substance used to soften plastics and increase flexibility, eg dibutyl benzene-1,2-dicarboxylate |
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Term
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Definition
| Structural isomers which have the same carbon skeleton and the same functional group(s) but in which the functional groups are joined at different places on the carbon skeleton |
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Term
| Preparative chromatography |
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Definition
| A form of purification of organic compounds, involving chromatography on a relatively large scale |
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Term
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Definition
| The primary structure of a protein is the sequence of amino acid units present in the polymer |
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Term
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Definition
| A substance that accepts protons in a chemical reaction |
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Term
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Definition
| Simplified NMR spectra obtained as a result of removing the interactions between C-13 nuclei and any attached protons |
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Term
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Definition
| A substance that donates protons in a chemical reaction |
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Term
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Definition
| In NMR, a peak that is split into 4 parts |
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Term
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Definition
| A mixture containing equal amounts of both enantiomers |
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Term
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Definition
| A positively-charged species which possesses an unpaired electron |
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Term
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Definition
| The constant of proportionality in the rate equation |
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Term
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Definition
| The slowest step in a multi-step reaction sequence |
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Term
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Definition
| The relationship between the rate of reaction and the concentration of reactants |
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Term
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Definition
| A sequence of discrete chemical reaction steps that can be deduced from the experimentally observed rate equation |
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Term
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Definition
| The processing of used materials, eg glass, paper, textiles, metals and plastics, into new products in order to prevent wastage, to reduce the consumption of raw materials and to lower energy costs |
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Term
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Definition
| The group of atoms that repeats throughout the length of a polymer chain |
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Term
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Definition
The separation or enantiomers
OR
The separation of chemicals using chromatography |
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Term
|
Definition
A concept used when a single molecule can be approximated by more than one classical Lewis structure, involving single and multiple covalent bonds
OR
In NMR, the excitation of atomic nuclei in a magnetic field by exposure to electromagnetic radiation of a specific frequency |
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Term
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Definition
| The increase in stability associated with resonance between Lewis structures |
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Term
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Definition
| A representation of an actual molecule, eg Benzene, when classical structures using single and multiple covalent bonds are inadequate |
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Term
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Definition
In chromatography
Rf = (distance travelled by compound)/(distance travelled by solvent front) |
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Term
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Definition
| In chromatography, the time each component remains in the column |
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Term
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Definition
| Of a protein, relates to the orderly, hydrogen-bonded arrangements between peptide chains resulting in either a helix or a pleated sheet |
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Term
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Definition
| In NMR, a nucleus is said to be shielded when the electron density surrounding it is increased, giving rise to an upfield shift (smaller δ value) |
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Term
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Definition
| In NMR, a peak that is not split |
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Term
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Definition
| In paper chromatography, the position reached by the leading edge of the solvent after separation has occured |
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Term
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Definition
| In NMR, the interaction between the nuclear spins of non-equivalent hydrogen atoms on adjacent carbon atoms |
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Term
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Definition
| In NMR, the splitting of an absorption signal (a peak) into more complex patterns as a result of coupling between neighbouring nuclear spins |
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Term
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Definition
| In chromatography, the fixed phase through which passes the moving or mobile phase |
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Term
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Definition
| Occurs when molecules with the same structural formula have bonds arranged differently in space |
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Term
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Definition
| Are compounds which have the same structural formula but have bonds arranged differently in space |
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Term
| Stoichiometric coefficient |
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Definition
| The number of moles of a species as shown in a balanced chemical equation |
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Term
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Definition
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Term
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Definition
| One that is completely dissociated in aqueous solution |
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Term
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Definition
| Occurs when the component atoms are arranged differently in molecules having the same molecular formula |
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Term
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Definition
| Compounds with the same molecular formula but different structures |
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Term
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Definition
| A wetting agent, containing hydrophobic and hydrophilic groups, able to lower the surface tension of a liquid and the interfacial tension between two liquids; the name is derived from surface acting agent |
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Term
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Definition
| A polyester, used in permanent-press fabrics, derived from benzene-1,4-dicarboxylic (terephthalic) acid and ethane-1,2-diol |
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Term
| Thin-layer chromatography |
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Definition
| Involves a thin layer of a polar, adsorbent material coated on to a glass plate or on to an aluminium or plastic sheet (the stationary phase) and a solvent (the moving phase) |
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Term
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Definition
| A plot of the pH of an acid/base against the volume of base/acid added |
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Term
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Definition
| A reversible reaction in which an ester reacts with an alcohol, usually in excess, to form a new ester and a new alcohol |
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Term
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Definition
| In NMR, a peak that is split into three parts |
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Term
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Definition
| A first-order step in a reaction mechanism |
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Term
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Definition
| The old name for ethenyl (-CH=CH2) |
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Term
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Definition
When Ka is small,
Ka ≈ [H+]2/[HA] |
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Term
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Definition
| One that is only partially dissociated in aqueous solution |
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Term
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Definition
| A dipolar ion that has both a positive and a negative charge, especially an amino acid in neutral solution |
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