Unit 4 key words – Flashcards
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| Acid-base equilibrium |
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| The equilibrium transfer of a proton from an acid to a base |
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| Acid dissociation constant (Ka) |
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| The equilibrium constant for the dissociation of a weak acid in water: Ka = (H+)(A-)/(HA) |
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| Acidic buffer |
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| A buffer that maintains a pH value below 7 |
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| Activation energy |
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| The minimum energy required for a reaction to occur |
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| Acyl group |
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| A functional group RC=O derived from a carboxylic acid |
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| Acylation |
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| The introduction of an acyl group into an organic molecule |
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| Acylium cation |
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| The electrophile [RCO]+ |
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| Addition polymer |
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| A polymer obtained by the addition of monomers to the end of a growing chain (alkenes) |
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| Adsorption Chromatography |
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| 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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| Amino acid |
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| 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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| Analytical chromatography |
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| 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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| Arenes |
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| Monocyclic or polycyclic aromatic hydrocarbons, such as benzene |
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| Aromatic |
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| The name traditionally used in relation to benzene and its derivatives |
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| Asymmetric carbon atom |
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| A carbon atom with four different atoms or groups attached that is devoid of symmetry |
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| Base peak |
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| The largest peak in a mass spectrum |
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| Basic buffer |
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| A buffer that maintains a pH value above 7 |
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| Bimolecular step |
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| A second-order step in a reaction mechanism |
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| Biodegradable |
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| Capable of being broken down by micro-organisms (enzymes) |
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| Biodiesel |
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| A renewable, non-petroleum-based fuel obtained by transesterification from vegetable oils, such as soya bean and rapeseed oil |
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| Bronsted–Lowry acid |
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| A proton donor |
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| Bronsted–Lowry base |
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| A proton acceptor |
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| Buffer range |
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| The pH range over which a weak acid/base can show buffer action |
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| Buffer region |
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| The concentration range over which a weak acid/base can show buffer action |
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| Buffer solution |
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| A solution that resists change in pH on addition of small amounts of acid or base, or on dilution |
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| Carrier gas |
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| An eluent gas, such as helium, used as the moving phase in gas-liquid chromatography |
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| Catalyst |
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| A substance that alters the rate a of reaction without itself being consumed |
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| Chain-growth polymer |
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| Addition polymer. A polymer obtained by the addition of monomers to the end of a growing chain (alkenes) |
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| Chain isomers |
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| Structural isomers which occur when there is more than one way of arranging the carbon skeleton of a molecule |
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| Chemical Shift |
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| 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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| Chiral drugs |
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| Drugs possessing chiral centres, often single-enantiomer structures |
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| Chiral molecule |
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| A molecule that cannot be superimposed on its mirror image |
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| Chromatogram |
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| A separated pattern of substances in a mixture, obtained by chromatography |
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| Chromatograph |
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| An apparatus used for chromatographic separation of volatile components in a mixture |
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| Chromatography |
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| 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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| Column Chromatography |
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| 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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| Condensation polymer |
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| A polymer involving the loss of small molecules, obtained by the reaction between molecules having two functional groups |
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| Delocalisation energy |
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| The increase in stability associated with electron delocalisation |
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| Delocalised electrons |
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| 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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| Deshielded |
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| In NMR, a nucleus is said to be deshielded when the electron density surrounding it is reduced, giving rise to a downfield shift (larger ? value) |
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| Diacidic Base |
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| A base that forms two moles of hydroxide ions per mole of base, eg Ba(OH)2 |
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| Diazotisation |
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| The conversion of ArNH2 into ArN2+ |
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| Diprotic Acid |
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| An acid that forms two moles of protons per mole of acid, eg H2SO4 |
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| Doublet |
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| In NMR, a peak that is split into 2 parts |
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| Ecoflex |
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| 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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| Electrophile |
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| 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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| Electrophilic substitution reaction |
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| Mechanistically, an electrophilic addition-elimination reaction resulting in overall substitution, typically involving arenes, eg Nitration of Benzene |
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| Eluate |
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| The solution emerging from a chromatographic column |
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| Eluent |
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| The solvent used as the moving phase in column chromatography |
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| Elution |
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| The process of washing the components of a mixture down a chromatographic column |
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| Enantiomers |
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| Three-dimensional, non-superimposable molecular structure mirror images |
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| Endothermic change |
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| A change in which heat energy is taken in |
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| End-point |
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| The point during a titration when the colour of an indicator lies half-way between the acid and base colours |
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| Equilibrium constant (Kc) |
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| 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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| Equivalence point |
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| The point on a titation curve at which stoichiometrically equivalent amounts of acid and base have been mixed together |
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| Exothermic change |
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| A change in which heat energy is given out |
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| E-Z stereoisomerism |
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| Also known as geometrical or cis-trans isomerism |
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| E-Z stereoisomers |
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| 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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| Fibrous proteins |
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| Contain long chains of polypeptides which occur in bundles, eg Keratin |
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| Fragmentation |
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| In mass spectrometry, the breakdown of a molecular ion into smaller, positively-charged ions and radicals |
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| Free-radical substitution reaction |
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| 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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| Friedel-Crafts acylation |
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| An electrophilic substitution reaction, involving an acylium cation, resulting in carbon-carbon bond formation |
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| Functional group |
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| An atom or group of atoms which, when present in different molecules, results in similar chemical properties |
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| Functional group isomers |
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| Structural isomers which contain different functional groups |
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| Gas-liquid chromatography |
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| 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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| Glass-transition temperature |
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| 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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| Globular proteins |
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| Contains long chains of amino acids, soluble in water, which are folded into roughly spherical shapes, eg haemoglobin |
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| Good leaving group |
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| A stable species which is liberated during an organic chemical reaction |
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| Half-equivalence |
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| 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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| Heterogenous system |
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| A system with the species present in different phases |
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| Heteronuclear species |
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| Molecules composed of more than one type of element, eg HCl |
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| Homogenous system |
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| A system with all species present in the same phase |
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| Homologous series |
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| 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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| Homonuclear species |
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| Diatomic molecules composed of only one type of element, eg Cl2 |
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| In vivo |
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| Within the human body |
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| Incineration |
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| Waste-treatment technology involving the combustion of organic materials |
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| Indicator |
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| Usually a weak organic acid with strongly coloured acid and base forms |
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| Initial rate of reacion |
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| The rate of change of concentration at the start of a reaction |
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| Integration trace |
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| 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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| Ionic product of water (Kw) |
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| Kw = [H+]*[OH-] |
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| Isoelectric point |
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| The pH at which an amino acid has no net charge |
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| Isomers |
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| Molecules with the same chemical formula but in which the atoms are arranged differently |
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| Kevlar |
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| 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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| Landfill site |
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| An area of land on which rubbish is dumped |
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| Le Chatelier's principle |
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| States that a system at equilibrium will respond to oppose any changes imposed upon it |
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| Magnetic moment |
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| A measure of the torque exerted on a magnetic system, eg a bar magnet, when placed in a magnetic field |
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| Mobile phase |
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| Moving phase; in chromatography, the liquid or gaseous phase that passes through a fixed stationary phase. |
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| Molecular ion (M+•) |
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| The species formed in a mass spectrometer by the loss of one electron from a molecule |
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| Monoacidic base |
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| A base that forms one mole of hydroxide ions per molecule of base, eg NaOH |
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| Monoprotic acid |
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| An acid that forms one mole of protons per mole of acid, eg HCl |
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| Moving phase |
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| Mobile phase; in chromatography, the liquid or gaseous phase that passes through a fixed stationary phase. |
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| Multiplet |
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| In NMR, a peak that is split into many parts |
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| n+1 rule |
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| In NMR, signals for protons adjacent to n equivalent neighbours are split into n+1 peaks |
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| Nitryl cation |
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| The electrophile +NO2 |
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| Nomex |
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| The 1,3-linked ismoer of Kevlar, used in flame-resistant clothing |
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| Nuclear spin |
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| 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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| Nucleophile |
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| An electron-rich molecule or ion able to donate a pair of electrons |
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| Nucleophilic addition reaction |
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| 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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| Optical isomers |
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| Stereoisomers (enantiomers) which rotate the plane of plane-polarised light equally but in opposite directions |
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| Optically active |
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| Capable of rotating the plane of plane-polarised light |
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| Order of reaction |
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| The sum of the powers of the concentration terms in the rate equation |
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| Paper chromatography |
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| 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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| Parent ion |
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| Molecular ion; The species formed in a mass spectrometer by the loss of one electron from a molecule |
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| Partition chromatography |
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| 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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| Peptide link |
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| The -CONH- linking group |
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| pH |
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| pH = -logKa |
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| pH at half equivalence |
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| At half equivalence, pH = pKa for a weak acid |
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| pKa |
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| pKa = -logKa |
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| Plasticiser |
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| A substance used to soften plastics and increase flexibility, eg dibutyl benzene-1,2-dicarboxylate |
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| Position isomers |
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| 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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| Preparative chromatography |
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| A form of purification of organic compounds, involving chromatography on a relatively large scale |
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| Primary structure |
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| The primary structure of a protein is the sequence of amino acid units present in the polymer |
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| Proton acceptor |
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| A substance that accepts protons in a chemical reaction |
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| Proton-decoupled spectra |
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| Simplified NMR spectra obtained as a result of removing the interactions between C-13 nuclei and any attached protons |
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| Proton donor |
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| A substance that donates protons in a chemical reaction |
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| Quartet |
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| In NMR, a peak that is split into 4 parts |
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| Racemate/Racemic mixture |
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| A mixture containing equal amounts of both enantiomers |
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| Radical cation |
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| A positively-charged species which possesses an unpaired electron |
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| Rate constant (k) |
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| The constant of proportionality in the rate equation |
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| Rate-determining step |
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| The slowest step in a multi-step reaction sequence |
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| Rate equation |
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| The relationship between the rate of reaction and the concentration of reactants |
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| Reaction mechanism |
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| A sequence of discrete chemical reaction steps that can be deduced from the experimentally observed rate equation |
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| Recycling |
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| 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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| Repeating unit |
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| The group of atoms that repeats throughout the length of a polymer chain |
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| Resolution |
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| The separation or enantiomers OR The separation of chemicals using chromatography |
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| Resonance |
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| 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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| Resonance energy |
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| The increase in stability associated with resonance between Lewis structures |
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| Resonance hybrid |
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| A representation of an actual molecule, eg Benzene, when classical structures using single and multiple covalent bonds are inadequate |
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| Retention factor (Rf) |
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| In chromatography Rf = (distance travelled by compound)/(distance travelled by solvent front) |
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| Retention time |
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| In chromatography, the time each component remains in the column |
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| Secondary structure |
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| 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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| Shielded |
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| In NMR, a nucleus is said to be shielded when the electron density surrounding it is increased, giving rise to an upfield shift (smaller ? value) |
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| Singlet |
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| In NMR, a peak that is not split |
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| Solvent front |
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| In paper chromatography, the position reached by the leading edge of the solvent after separation has occured |
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| Spin-spin coupling |
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| In NMR, the interaction between the nuclear spins of non-equivalent hydrogen atoms on adjacent carbon atoms |
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| Splitting |
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| 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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| Stationary phase |
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| In chromatography, the fixed phase through which passes the moving or mobile phase |
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| Stereoisomerism |
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| Occurs when molecules with the same structural formula have bonds arranged differently in space |
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| Stereoisomers |
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| Are compounds which have the same structural formula but have bonds arranged differently in space |
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| Stoichiometric coefficient |
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| The number of moles of a species as shown in a balanced chemical equation |
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| Stoichiometric point |
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| Equivalence point |
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| Strong acid/base |
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| One that is completely dissociated in aqueous solution |
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| Structural isomerism |
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| Occurs when the component atoms are arranged differently in molecules having the same molecular formula |
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| Structural isomers` |
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| Compounds with the same molecular formula but different structures |
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| Surfactant |
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| 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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| Terylene |
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| A polyester, used in permanent-press fabrics, derived from benzene-1,4-dicarboxylic (terephthalic) acid and ethane-1,2-diol |
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| Thin-layer chromatography |
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| 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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| Titration curve |
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| A plot of the pH of an acid/base against the volume of base/acid added |
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| Transesterification |
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| 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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| Triplet |
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| In NMR, a peak that is split into three parts |
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| Unimolecular step |
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| A first-order step in a reaction mechanism |
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| Vinyl |
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| The old name for ethenyl (-CH=CH2) |
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| Weak acid approximation |
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| When Ka is small, Ka ? [H+]2/[HA] |
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| Weak acid/base |
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| One that is only partially dissociated in aqueous solution |
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| Zwitterion |
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| A dipolar ion that has both a positive and a negative charge, especially an amino acid in neutral solution |
