Unit 4 key words Flashcard

Acid-base equilibrium
The equilibrium transfer of a proton from an acid to a base
Acid dissociation constant (Ka)
The equilibrium constant for the dissociation of a weak acid in water:

Ka = (H+)(A-)/(HA)

Acidic buffer
A buffer that maintains a pH value below 7
Activation energy
The minimum energy required for a reaction to occur
Acyl group
A functional group RC=O derived from a carboxylic acid
The introduction of an acyl group into an organic molecule
Acylium cation
The electrophile [RCO]+
Addition polymer
A polymer obtained by the addition of monomers to the end of a growing chain (alkenes)
Adsorption Chromatography
Involves a solid phase of finely-divided particles as the fixed (stationary) phase and a liquid or gas as the moving (mobile) phase
Amino acid
The name commonly used for compounds having a primary amino group attached to the carbon atom adjacent to a carboxylic acid group
Analytical chromatography
Operates with small amounts of material and aims to identify and measure the relative proportions of the various components present in a mixture
Monocyclic or polycyclic aromatic hydrocarbons, such as benzene
The name traditionally used in relation to benzene and its derivatives
Asymmetric carbon atom
A carbon atom with four different atoms or groups attached that is devoid of symmetry
Base peak
The largest peak in a mass spectrum
Basic buffer
A buffer that maintains a pH value above 7
Bimolecular step
A second-order step in a reaction mechanism
Capable of being broken down by micro-organisms (enzymes)
A renewable, non-petroleum-based fuel obtained by transesterification from vegetable oils, such as soya bean and rapeseed oil
Bronsted–Lowry acid
A proton donor
Bronsted–Lowry base
A proton acceptor
Buffer range
The pH range over which a weak acid/base can show buffer action
Buffer region
The concentration range over which a weak acid/base can show buffer action
Buffer solution
A solution that resists change in pH on addition of small amounts of acid or base, or on dilution
Carrier gas
An eluent gas, such as helium, used as the moving phase in gas-liquid chromatography
A substance that alters the rate a of reaction without itself being consumed
Chain-growth polymer
Addition polymer. A polymer obtained by the addition of monomers to the end of a growing chain (alkenes)
Chain isomers
Structural isomers which occur when there is more than one way of arranging the carbon skeleton of a molecule
Chemical Shift
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
Chiral drugs
Drugs possessing chiral centres, often single-enantiomer structures
Chiral molecule
A molecule that cannot be superimposed on its mirror image
A separated pattern of substances in a mixture, obtained by chromatography
An apparatus used for chromatographic separation of volatile components in a mixture
A technique for separating the components of a mixture on the basis of their different affinities for a stationary and a moving phase
Column Chromatography
Involves a stationary phase of finely-divided alumina or silica gel in a vertical glass tube and an organic solvent as the moving phase
Condensation polymer
A polymer involving the loss of small molecules, obtained by the reaction between molecules having two functional groups
Delocalisation energy
The increase in stability associated with electron delocalisation
Delocalised electrons
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
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)
Diacidic Base
A base that forms two moles of hydroxide ions per mole of base, eg Ba(OH)2
The conversion of ArNH2 into ArN2+
Diprotic Acid
An acid that forms two moles of protons per mole of acid, eg H2SO4
In NMR, a peak that is split into 2 parts
A fully biodegradable aliphatic-aromatic co-polyester, used for disposable packaging, based on butane-1,4-diol and benzene-1,4-dicarboxylic acid
An electron-seeking species, eg a positive ion or the more positive end of a polar molecule, which usually accepts a pair of electrons
Electrophilic substitution reaction
Mechanistically, an electrophilic addition-elimination reaction resulting in overall substitution, typically involving arenes, eg Nitration of Benzene
The solution emerging from a chromatographic column
The solvent used as the moving phase in column chromatography
The process of washing the components of a mixture down a chromatographic column
Three-dimensional, non-superimposable molecular structure mirror images
Endothermic change
A change in which heat energy is taken in
The point during a titration when the colour of an indicator lies half-way between the acid and base colours
Equilibrium constant (Kc)
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

Equivalence point
The point on a titation curve at which stoichiometrically equivalent amounts of acid and base have been mixed together
Exothermic change
A change in which heat energy is given out
E-Z stereoisomerism
Also known as geometrical or cis-trans isomerism
E-Z stereoisomers
Arise due to restricted rotation about carbon-carbon double bonds when the two pairs of attached substituents can be arranged in 2 different ways
Fibrous proteins
Contain long chains of polypeptides which occur in bundles, eg Keratin
In mass spectrometry, the breakdown of a molecular ion into smaller, positively-charged ions and radicals
Free-radical substitution reaction
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)
Friedel-Crafts acylation
An electrophilic substitution reaction, involving an acylium cation, resulting in carbon-carbon bond formation
Functional group
An atom or group of atoms which, when present in different molecules, results in similar chemical properties
Functional group isomers
Structural isomers which contain different functional groups
Gas-liquid chromatography
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)
Glass-transition temperature
The temperature at which a polymer changes from a hard and glass-like state to a more flexible and mouldable state
Globular proteins
Contains long chains of amino acids, soluble in water, which are folded into roughly spherical shapes, eg haemoglobin
Good leaving group
A stable species which is liberated during an organic chemical reaction
When exactly one-half of the equivalence volume of a base or acid has been added to an acid or base
Heterogenous system
A system with the species present in different phases
Heteronuclear species
Molecules composed of more than one type of element, eg HCl
Homogenous system
A system with all species present in the same phase
Homologous series
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
Homonuclear species
Diatomic molecules composed of only one type of element, eg Cl2
In vivo
Within the human body
Waste-treatment technology involving the combustion of organic materials
Usually a weak organic acid with strongly coloured acid and base forms
Initial rate of reacion
The rate of change of concentration at the start of a reaction
Integration trace
In NMR, a computer-generated line, sumperimposed on the spectrum, which measures the relative areas under the various peaks in the spectrum
Ionic product of water (Kw)
Kw = [H+]*[OH-]
Isoelectric point
The pH at which an amino acid has no net charge
Molecules with the same chemical formula but in which the atoms are arranged differently
A sheet-like polyamide, used in bullet-proof vests, derived from benzene-1,4-dicarboxylic acid and benzene-1,4-diamine
Landfill site
An area of land on which rubbish is dumped
Le Chatelier’s principle
States that a system at equilibrium will respond to oppose any changes imposed upon it
Magnetic moment
A measure of the torque exerted on a magnetic system, eg a bar magnet, when placed in a magnetic field
Mobile phase
Moving phase; in chromatography, the liquid or gaseous phase that passes through a fixed stationary phase.
Molecular ion (M+•)
The species formed in a mass spectrometer by the loss of one electron from a molecule
Monoacidic base
A base that forms one mole of hydroxide ions per molecule of base, eg NaOH
Monoprotic acid
An acid that forms one mole of protons per mole of acid, eg HCl
Moving phase
Mobile phase; in chromatography, the liquid or gaseous phase that passes through a fixed stationary phase.
In NMR, a peak that is split into many parts
n+1 rule
In NMR, signals for protons adjacent to n equivalent neighbours are split into n+1 peaks
Nitryl cation
The electrophile +NO2
The 1,3-linked ismoer of Kevlar, used in flame-resistant clothing
Nuclear spin
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
An electron-rich molecule or ion able to donate a pair of electrons
Nucleophilic addition reaction
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
Optical isomers
Stereoisomers (enantiomers) which rotate the plane of plane-polarised light equally but in opposite directions
Optically active
Capable of rotating the plane of plane-polarised light
Order of reaction
The sum of the powers of the concentration terms in the rate equation
Paper chromatography
Involves a thin layer of water adsorbed onto chromatographic paper (the stationary phase) and a solvent or solvent mixture (the moving phase)
Parent ion
Molecular ion; The species formed in a mass spectrometer by the loss of one electron from a molecule
Partition chromatography
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)
Peptide link
The -CONH- linking group
pH = -logKa
pH at half equivalence
At half equivalence, pH = pKa for a weak acid
pKa = -logKa
A substance used to soften plastics and increase flexibility, eg dibutyl benzene-1,2-dicarboxylate
Position isomers
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
Preparative chromatography
A form of purification of organic compounds, involving chromatography on a relatively large scale
Primary structure
The primary structure of a protein is the sequence of amino acid units present in the polymer
Proton acceptor
A substance that accepts protons in a chemical reaction
Proton-decoupled spectra
Simplified NMR spectra obtained as a result of removing the interactions between C-13 nuclei and any attached protons
Proton donor
A substance that donates protons in a chemical reaction
In NMR, a peak that is split into 4 parts
Racemate/Racemic mixture
A mixture containing equal amounts of both enantiomers
Radical cation
A positively-charged species which possesses an unpaired electron
Rate constant (k)
The constant of proportionality in the rate equation
Rate-determining step
The slowest step in a multi-step reaction sequence
Rate equation
The relationship between the rate of reaction and the concentration of reactants
Reaction mechanism
A sequence of discrete chemical reaction steps that can be deduced from the experimentally observed rate equation
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
Repeating unit
The group of atoms that repeats throughout the length of a polymer chain
The separation or enantiomers
The separation of chemicals using chromatography
A concept used when a single molecule can be approximated by more than one classical Lewis structure, involving single and multiple covalent bonds
In NMR, the excitation of atomic nuclei in a magnetic field by exposure to electromagnetic radiation of a specific frequency
Resonance energy
The increase in stability associated with resonance between Lewis structures
Resonance hybrid
A representation of an actual molecule, eg Benzene, when classical structures using single and multiple covalent bonds are inadequate
Retention factor (Rf)
In chromatography

Rf = (distance travelled by compound)/(distance travelled by solvent front)

Retention time
In chromatography, the time each component remains in the column
Secondary structure
Of a protein, relates to the orderly, hydrogen-bonded arrangements between peptide chains resulting in either a helix or a pleated sheet
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)
In NMR, a peak that is not split
Solvent front
In paper chromatography, the position reached by the leading edge of the solvent after separation has occured
Spin-spin coupling
In NMR, the interaction between the nuclear spins of non-equivalent hydrogen atoms on adjacent carbon atoms
In NMR, the splitting of an absorption signal (a peak) into more complex patterns as a result of coupling between neighbouring nuclear spins
Stationary phase
In chromatography, the fixed phase through which passes the moving or mobile phase
Occurs when molecules with the same structural formula have bonds arranged differently in space
Are compounds which have the same structural formula but have bonds arranged differently in space
Stoichiometric coefficient
The number of moles of a species as shown in a balanced chemical equation
Stoichiometric point
Equivalence point
Strong acid/base
One that is completely dissociated in aqueous solution
Structural isomerism
Occurs when the component atoms are arranged differently in molecules having the same molecular formula
Structural isomers`
Compounds with the same molecular formula but different structures
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
A polyester, used in permanent-press fabrics, derived from benzene-1,4-dicarboxylic (terephthalic) acid and ethane-1,2-diol
Thin-layer chromatography
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)
Titration curve
A plot of the pH of an acid/base against the volume of base/acid added
A reversible reaction in which an ester reacts with an alcohol, usually in excess, to form a new ester and a new alcohol
In NMR, a peak that is split into three parts
Unimolecular step
A first-order step in a reaction mechanism
The old name for ethenyl (-CH=CH2)
Weak acid approximation
When Ka is small,
Ka ? [H+]2/[HA]
Weak acid/base
One that is only partially dissociated in aqueous solution
A dipolar ion that has both a positive and a negative charge, especially an amino acid in neutral solution

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