Definitions A level Flashcards
Chiral Carbon
an asymmetric carbon atom/ a carbon atom bound to 4 different groups. This may also be called a chiral centre.
Displayed Formula
shows all the bonds between every atom in the compound.
Enantiomers
molecules which are non-superimposable mirror images of one another. Enantiomers have different effects on a plane of polarised light.
Optical isomerism
a type of stereoisomerism that occurs as a result of the presence of a chiral centre in a molecule. Optical isomers have different effects on a plane of polarised light.
Racemic Mixture (racemate)
a mixture containing equal amounts of enantiomers.
Stereoisomers
compounds that only differ in their arrangement of atoms in space.
Structural Formula
shows the arrangement of atoms in a molecule without the bonds drawn between them.
E.g.CH3 CH2 COCH3.
Aldehyde
a molecule containing the C=O functional group at the end of the molecule. Aldehydes can be distinguished from ketones using Fehling’s solution or Tollens’ reagent. Aldehydes produce a silver mirror with Tollens’ and a red precipitate with Fehling’s solution. Ketones do not react with either of these reagents.
Carbonyl group
a functional group with a C=O double bond.
Curly Arrow
used in mechanisms to show the movement of a pair of electrons
Hydroxynitrile
a molecule containing an alcohol group (OH) and a nitrile group (C≡N) bound to the same carbon. These can be formed in a nucleophilic addition reaction between a carbonyl and KCN followed by dilute acid (this reaction forms a mixture of enantiomers if an aldehyde or an unsymmetrical ketone is used).
Ketone
a molecule containing the C=O functional group in the middle of the molecule. Ketones can be distinguished from aldehydes using Fehling’s solution or Tollens’ reagent. Ketones do not react with either of these reagents while aldehydes produce a silver mirror with Tollens’ and a red precipitate with Fehling’s solution.
Nucleophile
an electron pair donor.
Nucleophilic Addition
a reaction in which an electrophilic π bond reacts with a nucleophile,
breaking the π bond and forming 2 new σ bonds.
Oxidation of Aldehydes
aldehydes can be oxidised using acidified potassium dichromate to form carboxylic acids.
Reduction of Aldehydes
aldehydes can be reduced to primary alcohols in a nucleophilic addition reaction with NaBH4 in aqueous solution.
Reduction of Ketones
ketones can be reduced to secondary alcohols in a nucleophilic addition reaction with NaBH4 in aqueous solution.
Alcohol
a molecule containing the OH functional group.
Biodiesel
a mixture of methyl esters of long-chain carboxylic acids. Biodiesel is produced by
reacting vegetable oils with methanol in the presence of a catalyst.
Carboxylic Acids
molecules containing the -COOH functional group. Carboxylic acids are weak acids that form CO2 when reacted with carbonates.
Esters
molecules containing the R-COO-R’ functional group which can be formed when carboxylic acids and alcohols react in the presence of an acid catalyst. Esters of glycerol (propane-1,2,3-triol) naturally occur in vegetable oils and animal fats and these esters can be hydrolysed in alkaline conditions to produce soaps and glycerol. Esters can be used to create solvents, plasticisers, perfumes and food flavourings.
Melting Point Apparatus
a piece of apparatus used to determine the melting point of a sample. The recorded melting point range is compared with known values to determine whether the sample is pure.
Hydrolysis of esters
under acidic conditions, esters will be hydrolysed to form alcohols and carboxylic acids. Under alkaline conditions, esters will be hydrolysed to form alcohols and carboxylate salts.
Nucleophile
an electron pair donor
Nucleophilic addition-elimination
a reaction in which a nucleophile is added to a molecule by breaking a π bond then a leaving group is removed to reform the π bond.
Primary Amide
a molecule containing the functional group shown below.
Recrystallisation
a technique used to purify a compound. A sample is dissolved in the minimum volume of hot solvent then filtered. The filtrate is then cooled before being filtered under reduced pressure. The residue on the filter paper is the purified compound.
Acyl Group
a group with the structure shown below, where R is an alkyl group.
Addition Reaction
a reaction in which molecules combine to form a single product.
Aromatic Compound
a compound containing at least one benzene ring.
Benzene
a 6 membered carbon ring (C6 H 6 ) containing a delocalised π system. Benzene has a planar structure and a bond length between a single and double bond. Delocalisation of the p electrons into the π system makes benzene more stable than expected.
Delocalisation of p electrons
in benzene, the empty p orbital on each carbon atom overlaps with the others to form a delocalised π system which contains 6 electrons.
Electrophile
an electron pair acceptor.
Electrophilic Substitution
a reaction in which an electrophile replaces an atom / group of atoms in a compound.
Enthalpy of Hydrogenation
the enthalpy change that takes place when one mole of an unsaturated compound reacts completely with hydrogen to form a saturated compound. Comparing the enthalpy of hydrogenation of benzene with that of the theoretical molecule cyclohexa-1,3,5-triene shows that benzene is more thermodynamically stable as more energy is needed to hydrogenate benzene.
Friedel-Crafts Acylation
an important synthetic reaction involving an electrophilic aromatic substitution reaction between benzene and acyl chlorides or anhydrides, used to form monoacylated benzene rings. AlCl3 is used as a catalyst.
Monosubstituted benzene ring
a benzene ring with one hydrogen replaced by another group,
e.g. C6 H5 NO2
Nitration
Nitration is important for synthesis, particularly for manufacturing explosives and for forming amines. Benzene can undergo nitration via an electrophilic substitution reaction, using concentrated nitric acid and a concentrated sulfuric acid catalyst at 50°C.
Substitution Reaction
a reaction in which one atom/ group of atoms is replaced by another atom / group of atoms.
Aliphatic
organic compounds with carbon atoms joined in chains.
Aromatic
a compound containing at least one benzene ring.
Amines
compounds based on ammonia where hydrogen atoms have been replaced by alkyl or aryl groups. Amines are weak bases that can act as nucleophiles.
Alkyl group
a group based on an alkane, where one hydrogen has been removed (this allows the group to attach to another atom in a chain).
Lone Pair
a pair of valence electrons (outer-shell electrons) not involved in bonding.
Nucleophilic substitution
a reaction in which an electron-rich nucleophile attacks a positive charge or partial positive charge to replace an atom/ group of atoms. One example of this is the reaction between ammonia and halogenoalkanes, which forms a primary ammonium salt.
Primary aliphatic amines
an organic compound with the structure R-NH2 (where R is an alkyl group). Primary aliphatic amines can be prepared by reacting ammonia with halogenoalkanes or by reducing nitriles.
Primary ammonium salt
n organic compound formed when a halogenoalkane is reacted with ammonia. These salts have the general formula RNH3 + X - (where R is an alkyl group and X- is the halide ion).
Secondary ammonium salt
an organic compound formed when a halogenoalkane reacts with a primary amine. These salts have the general formula R2 N H2 + X - (where R is an alkyl group and X- is the halide ion).
Tertiary ammonium salt
an organic compound formed when a halogenoalkane reacts with a secondary amine. These salts have the general formula R3 N H+ X - (where R is an alkyl group and X- is the halide ion).
Addition Polymer
a long chain molecule formed when many monomers join together, where the polymer is the only product.
Biodegradable
a substance that can be decomposed by bacteria or other living organisms.
Condensation Polymer
a long chain molecule formed when monomers react together with the release of small molecules such as water. These polymers can be formed by a reaction between dicarboxylic acids and diols, dicarboxylic acids and diamines or between amino acids.
Monomer
a small molecule that is used to form polymers.
Hydrolysis
a reaction which uses water to break down a compound.
Intermolecular Forces: forces which act between molecules. These include permanent dipole-dipole forces, induced dipole-dipole forces and hydrogen bonding.
Polyalkene
a type of addition polymer formed when many alkene monomers are joined together. These polymers are chemically inert and non-biodegradable.
Polyamide
a type of condensation polymer formed by the linkage of an amino group in one monomer and a carboxylic acid group of another (e.g. nylon 6,6 and Kevlar). These polymers can be broken down by hydrolysis and are biodegradable.
Polyester
a type of condensation polymer formed by the linkage of an alcohol group in one monomer with a carboxylic acid group of another (e.g. Terylene). These polymers can be broken down by hydrolysis and are biodegradable.
Polymer
a large molecule made from many small units that have been bonded together.
Repeating Unit
a structure within a polymer that appears over and over again. Joining many repeat units together would form the polymer.
Active Site
the region of an enzyme where the substrate binds.
Amino Acid
an organic compound containing both a carboxyl group (-COOH) and an amino group (-NH2).
Catalyst
a substance which speeds up the rate of a reaction without being used up. Enzymes are biological catalysts.
Cisplatin
a complex of PtIl) which is used as an anticancer drug. Cisplatin prevents DNA replication in cancer cells by a ligand replacement reaction with DNA (during this reaction, a bond forms between platinum and a nitrogen atom in guanine).
Developing Agents
these are used to locate amino acids on a chromatogram (e.g. ninhydrin and ultraviolet light).
DNA (deoxyribonucleic acid)
a polymer of nucleotide linked by covalent bonds between the phosphate group of one nucleotide and the 2-deoxyribose of another nucleotide. The resulting polymer has a sugar-phosphate-sugar-phosphate chain with the bases (adenine, cytosine, guanine and thymine) attached to the sugars in the chain. DNA has a double helix structure which is made up of 2 complementary strands.
Enantiomers
molecules that are non-superimposable mirror images of one another.
Enzyme: a biological catalyst made of proteins. Enzymes have stereospecific active sites that bind to a certain substrate molecule.
Enzyme Inhibitor
a substance that reduces the activity of an enzyme. This might be a drug which blocks the active site, preventing a substrate molecule binding.
Hydrogen Bonding:
a type of intermolecular bond formed between a hydrogen atom in one molecule and an electronegative atom in another. Hydrogen bonding between base pairs leads to complementary strands of DNA.
Enzyme
a biological catalyst made of proteins. Enzymes have stereospecific active sites that bind to a certain substrate molecule.
Hydrolysis
a reaction in which water is used to break a bond.
Nucleotide
a molecule made from a phosphate ion bound to 2-deoxyribose which is bonded to one of the 4 bases of DNA (adenine, cytosine, guanine and thymine).
Pentose Sugar
a sugar molecule that contains 5 carbon atoms.
Ligand
an ion or molecule that binds to a metal atom by donating a pair of electrons and forming a coordinate bond.
Primary Protein Structure
the sequence of a chain of amino acids that make up a protein, contains peptide bonds.
Peptide Link
a bond which forms between the carboxyl group (-COOH) of one amino acid and the amino group (-NH,) of another in a protein. When peptide links are hydrolysed, the constituent amino acids are formed.
Protein
a molecule made up of amino acids joined by peptide bonds. Hydrogen bonding and sulfur-sulfur bonds are important to maintain the structure of proteins.
Secondary Protein Structure
the structure of a protein when hydrogen bonds form between the amino acid chains. There are 2 types of secondary protein structure: a-helix and B-pleated sheet.
Substrate
a molecule that binds to the active site of an enzyme during a reaction.
Tertiary Protein Structure
the three dimensional structure of a protein. This contains ionic bonds, disulfide bridges, hydrogen bonding and induced dipole-dipole interactions.
Zwitterion
a molecule which has separate positively and negatively charged groups.
Aliphatic Compound
an organic compound that is made up of straight or branched chains.
Atom Economy
The measure of the amount of starting materials that end up as useful products.
Aliphatic Compound
an organic compound that is made up of straight or branched chains.
CCl4
a solvent commonly used in 1 H NMR spectroscopy.
Chemical Shift
the shift of a carbon or proton environment relative to standard (TMS). The chemical shift value (δ) depends on the molecular environment of the proton/ carbon atom.
Doublet
a signal on a 1 H NMR spectra made up of 2 peaks, indicating that there is 1 adjacent non-equivalent proton.
Equivalent protons
protons that are in the same environment.
Integrated NMR Spectrum
shows the area under each peak on a 1 H NMR spectrum,
indicating the relative number of 1 H atoms in each environment.
n+1 rule
used to determine spin-spin splitting patterns of adjacent non-equivalent protons. A proton with n adjacent non-equivalent protons will have a signal made up of n+1 peaks on a 1H NMR spectrum.
Nuclear Magnetic Resonance (NMR)
a technique that uses the absorption of electromagnetic radiation by a nucleus in an external magnetic field to analyse the structure of a compound. Typically, either 1 3C or 1 H nuclei are analysed. 1 3C NMR spectra are generally simpler than 1 H NMR spectra.
Quartet
a signal on a 1 H NMR spectra made up of 4 peaks, indicating that there are 3 adjacent non-equivalent protons.
Singlet
a signal on a 1 H NMR spectra made up of 1 peak, indicating that there are no adjacent non-equivalent protons.
TMS (tetramethlysilane)
the standard for calibrating chemical shift values in NMR.
Triplet
a signal on a 1 H NMR spectra made up of 3 peaks, indicating that there are 2
adjacent non-equivalent protons.
