Alkanes/enes Flashcards
What is the functional group
Part largely responsible for the molecules chemical properties
Homologous series
A series of organic compounds with same functional but differ by CH2
Structural isomers
Compunds with same molecular formula but different structural formula, can have same or different fucntional group at different points on chain
Homolyctic fission
Each of the covalently bonded atoms take one of the shared electrons, form8ng 2 radicals
Heterolytic
1 of the covalently bonded atoms takes both electrons, 1 becomes -ve ion and the other +ve ion
Curly arrow
Movement of pair of electrons
Substitution
Atom or group of atoms is replaced by a different atom/group
Addition
2 reactants join to make 1 product
Elimination
Removal of small molecule from a saturated molecule to form unsaturated molecule
Hydrogenation
Hydrogen in presence of nickel catalsyt at 150 c. breaks the pi bond, turns alkenes to alkanes
Electrophile
Accepts an electrons pair
Cracking
Decomposition of alkanes to obtain smaller chain alkanes and alkenes
Thermal cracking
Hight temp and pressure for short time
Catalytic cracking
Zeolute catalyst present ( eg. SO2, ALO) produce mainly branched alkanes
Thermal decomposition
Crude oil separated into different fractions
How to test for double bond
Alkene + bromine water = orange to colourless
What shape are cis/z isomers
U shaped, so dont pack well
Why do trans/e isomers have a lower boiling point that cis isomers
Trans are non polar so only contain london forces whereas cis are polar so contain london forces and permentant dipole-dipole interactions.
Why do trans isomers have a higher melting point than cis
Cis are U shaped so cant pack together well but trans can so the london forces in trans are closer togther therefore stronger
Sigma bonds
Are the overlapping of 2 S orbitals. Atoms can rotate freely around them
Pi bond
Overlapping of 2 P orbitals. Prevents rotation
3 steps of free radical substitution
Initiation
Propogation
Termination
Electrophillic addition
The double bond in alkene is an area of high electron density due to pi bond, so electrophiles are attracted to this area of high electrom denstity. The pi bond breaks due to it being attracted to a dipole on the reactant and then a carbocation is formed which will also atrract another molecule
How to make alcohol
Alkene + steam = alcohol
Conditionsa include acid catalyst H3PO4 ( phosphoric acid)
