organic

• stability of carbon cations increases as the number of R groups on the carbon cation increases because R groups are more electron donating than hydrogens which stabilises the positive charge of carbon
• alkenes are planar
• C-C and C-H bonds are made from overlap of sp2 orbitals on each C atom
• C-C pi bond is made from the overlap of the p orbital on each C atom
• alkenes have fixed stereochemistry, so we have E/Z geometric isomers
• when an unsymmetrical alkene reacts with an unsymmetrical reagent there are 2 possible products depending on which side of the double bond reacts with the electrophile although usually now product is given over the other (regioselectivity)
• Markovnikhov's Rule tells us that the H of a hydrogen halide ends up on the carbon of the alkene which has more hydrogens to start with.
• reactions between a cyclic alkene and X2 leads to the formation of a racemic mixture

  if the reactants are achiral/racemic the products will be achiral or racemic
• antiaddition - when on addition o fX2 to an alkene only one product is formed
• stereospecific

  description of reaction mechanism
• stereoselective

  description of reaction outcome
• alkenes + oxidation = epoxides
• an epoxide is a three membered ring ether (R1-O-R2)
• to synthesis epoxides the RO- nucleophile must attack via backside attack

  if backside attack can't occur (blocked my bulky groups) and epoxide will not be formed
• allylic - used to describe a compound when the double bond is one C-C bond away from the OH
• when an allylic alkene reacts with m-CPBA the pathway with more H bonding is favoured
• pathways involving steric hindrance are less favoured
• epoxides are highly reactive because of their ring strain and would be more stable if the strain were released by ring opening to restore the ideal tetrahedral angle at all atoms
• epoxides ring strain makes them good electrophiles and they can be ring opened by the attack of a nucleophile
• regioselectivity - bond formation favoured at particular carbon
• the regioselectivity of epoxides depends on whether a reaction occurs with a base or an acid
• Sn2 reaction pathways are stereospecific and always proceed with inversion of configuration
• regioselectivity may not occur if there is no steric hindrance
• when epoxides are ring opened in acidic conditions the oxygens lone pair attacks the more substituted end of the epoxide
• when epoxides are ring opened by an acid catalyst the reaction is not governed by steric hindrance but the reaction is still stereospecific and always proceeds with inversion of configuration
• an oxidation reaction is one where carbon loses electron density which happens when electrons are removed or when a new bond to a more electronegative atoms occurs
• a reduction reaction is one where carbon gains electron density, which happens when electrons are introduced or when hydrogen atoms are transferred to a molecule
• OsO4 is often used in small amounts because of its toxicity
• a meso compound has chiral centres but also an internal line of symmetry which cancels out these chiral centres so overall the molecule is achiral
• oxidative cleavage is the mechanism by which alkenes are transformed into aldehydes
• hydrogen is an excellent reducing agent
• heterogeneous catalysis - catalyst is in different phase from the reagents
• the carbonyl bond is slightly polarised creating a carbon electrophile
• Carbon electrophiles on tetrahedrons can be attacked from above or below (no facial selectivity) which produces a racemic mixture of R and S enantiomers
• The electrophilicity of the carbonyl bond (reactivity) will be greater if there are more electron withdrawing groups on the compound to help stabilise oxygens partially negative charge
• The electrophilicity of the carbonyl bond decreases as leaving group ability decreases
• an acyl group is an R group with an oxygen
• most stable anions make the best leaving groups
• Acid chlorides synthesised by the reaction between the corresponding carboxylic acid and thionyl chloride SOCl2
• Acid anhydrides are compounds that have two acyl groups bonded to the same oxygen atom