as level organic chem

alkane

saturated hydrocarboin containing only single carbon-carbon bonds, tetrahedral arrangement around c-c bond with 109.5 bond angle

alkene

unsaturated hydrocarbon containing double bonds between carbon atoms, trigonal planar arrangement around double bond with 120 bond angle

homologous series

family of compounds with similar chemical properties whose successive members differ by the addition of a ch2 group

sigma bond (present in both alkenes and alkanes)

direct overlap of bonding orbitals between bonding atoms can be c-c or c-h

pi bond (only in alkenes)

sideways overlap of 2p orbitals around the c=c double bond

3 stages of free radical substitution (alkanes)

initiation, propagation, termination

initiation

UV light breaks halogen molecules into free radicals by providing enough energy to overcome the strong covalent bond

propagation

halogen radicals react with alkanes in chain reactions where the halogen radical acts as a catalyst, pair of propagation steps for each h replaced

termination

any 2 free radicals meeting and reacting to form a molecule, stops chain reaction

free radical

atom with an unpaired electron (odd no. of electrons)

what happens to bpt when chian length increases

increases, molecules have greater sa so more surface contact resulting in greater london forces which require more energy to overcome

what happens to bpt as number of branches increases

decreases, less surface contact so weaker london forces which require less energy to overcome

homolytic fission

each bonded atom takes one of the shared pair of electrons, each atom is now an unstable radical

heterolytic fission

one of the bonded atoms takes both of the shared pair of electrons, each atom is now an ion

addition reaction

2 reactants join together to form 1 product

substitution reaction

atom or group of atoms replaced by different atom or group of atoms

elimination reaction

removal of a smaller molecule from a larger one

catenation

ability to form bonds between atoms of the same element e.g. carbon

aliphatic

straight or branched chains

alicyclic

ring/cyclic structure

aromatic

containing a benzene ring

isomer

molecules with same molecular formula but different structural arrangement of atoms

chain isomerism

molecule with same molecular formula but different arrangement of carbon skeleton

positional isomerism

molecules with same molecular formula but functional group in a different position

functional isomerism

molecules with same molecular formula but with atoms arranged into different functional groups e.g. aldehydes and ketones

electrophiles

atoms attracted to electron rich atoms where it accepts electron pairs

electrophilic addition mechanism (alkenes)

pi bond breaks and forms dative covalent bond with h, carbocation is formed, species that left now has a lone pair which acts as a nucleophile and forms a covalent bond with the carbocation

why are alkenes attacked by electrophiles

because of the electron density around the pi double bond

markownikoff’s rule

in the addition of a hydrogen halide to an alkene, the h attaches to the carbon with fewer alkyl groups and the halogen attached to the carbon with more alkyl groups

inductive effect

carbocation stability increases with increasing alkyl substituents because alkyl groups tend to donate electrons to the positively charged carbon atom

aliphatic alcohols

no ring, gen formula CnH2n+1OH

aromatic alcohol

OH attached directly to ring (phenols) not on alkyl group

alicyclic alcohol

OH on alkyl group of ring

trends in alcohol bpt

increases with size due to increased london forces because more surface contact and added presence of H bonding

why are alcohols soluble

due to the h bonding caused by the polar o-h bond

oxidation of primary alcohols

aldehyde: distill with acidified potassium dichromate, carboxylic acid: reflux with acidified potassium dichromate

oxidation of secondary alcohols

ketone, reflux with acidified potassium dichromate

oxidation of tertiary alcohols

do not undergo oxidation because unreactive

dehydration of alcohols

elimination reaction, reflux in presence of acid catalyst

substitution reaction of alcohols

reflux with sulfuric acid and sodium halide to form a hydrogen halide

stereoisomers

atoms are bonded in the same order but arranged differently in space

geometric isomersim

rotation prevented by double bond

optical isomerism

non-superimposable mirror images

hydrogenation of alkenes (h2)

nickel catalyst, 423K, produces alkane

halogenation of alkenes (halogen or hydrogen halide)

rtp, forms haloakane

hydration (h2o (g)) of alkenes

steam, phosphoric acid catalyst, forms alcohol

high density polyethene

linear chains, cain pack together tightly, stromg

low density polyethene

branched chains, can’t pack togetehr tightly, less stong, flexible

feedstock recycling

chemical and thermal processes reclaiming monomers, gases, or oil from waste polymers

bioplastics

made from plant starch, cellulose, oils and proteins, offer alternative to oil based products

biodegradable polymers

broken down by microoganisms into co2 and h2o and biological compounds, usually made from starch/cellulose + additives which allow it to be broken down

compostable polymers

degrade, leave no visible/toxic residuals

photodegradable polymers

contain bonds that are weakened by absorbing light and start the degradation

trend in boiling point of haloakanes

increases with molecular size due to increased intermolecular forces, increases for straight chain isomers but not branched isomers

solubility of haloalkanes

only soluble in organic solvents but insoluble in water

nucleophile

electron pair donors, possess at least 1 lone pair, attracted to electron deficient & slightly +ve carbon atoms

nucleophilic substitution mechanism

halogens more e negative than carbon which induces a dipole in their bond and it becomes polar, carbon open to attack by nucleophiles, requires aqueous naoh and heating under reflux because too slow at rt

trend in rate of hydrolysis of haloalkanes

as you go down group 7, it’s bond length with carbon increases resulting in lower bond enthwlpy so quicker rate of hydrolysis

properties of chlorofluorocarbons

non-flammable, non-toxic, low reactivity, high volatility

ozone layer (o3)

in stratosphere, absorbs uv radiation from sun

cfcs and the ozone layer

cfcs rise to stratosphere, uv light from sun provides energy to form cl radicals which react to destroy ozone in chain reaction (free radical substitution)

nitrogen oxide and ozone

formed in thunderstorms, break down to give nitrogen monoxide radical which catalyses ozone breakdown