products formed from complete combustion with alkenes
co2 and h2o
why are alkenes not used as fuels
presence of c=c bonds in alkenes make them more useful as starting material for manufacturing other important chemicals
function of pi electrons in ensuring that alkenes are reactive in c=c bond
attract electrophiles or induce dipole in approaching molecules to form electrophiles.
what is the product formed from the addition of halogens to alkenes, reagents and conditions, observations
dihalogenoalkanes, halogen in organic solvents at room temp, orange-red bromine decolourises
describe briefly electrophilic addition mechanism for alkenes
pi bond in alkene approaches the halogen and induces a dipole. The halogen atom with partial positive charge acts as an electrophiles.
The pi electrons in the c=c bond act as the nucleophile and approaches the partial positive halogen atom to form an unstable carbocation immediate and a halide ion.
The halide ion attacks the carbocation intermediate to form the dihalogenoalkane.
product formed from addition of halogens in water, and reagents and conditions, observations
halohydrins, aqueous halogen at room temp, orange bromine water decolourises
products formed, reagents and conditions as well as observations in the addition of hydrogen halides
halogenoalkanes, dry HX(g), at room temp, no observable change
why is the rate of reaction highest for HI, and lowest for HCl
HI has longest bond length, weakest bond strength, rate of reaction fastestm
explanation behind markonikov’s rule
electron donating effect of alkyl groups help to stabilize carbonation by dispersing the positive charge of the carbon atom. a carbonation with more alkyl groups more stable, and forms at a higher rate. more stable carbonation leads to major prod.
addition of steam to alkenes (hydration) product reagents and conditions, observations
alcohol, h2o(g), heat in presence of concentrated h3po4 catalyst at high temp and pressure, no observable change
reduction (catalytic hydrogenation) product reagents and conditions, observations
Hydrogen Gas and Ni Catalyst, product: alkanes, no observable change
mild oxidation product reagents and conditions, observations
product: diols
cold, alkaline KMnO4
observation: Purple KMnO4 decolourises, Brown Precipitate of MnO2 is formed
srong oxidation product(s) reagents and conditions, observations
products: carbon dioxide and water, carbonyl compounds or carboxylic acids
acidified KMnO4, heat under reflux
observation: purple KMnO4 decolurises
dehydration product(s) reagents and conditions, observations
alkene, H2O(g), conc H3PO4 catalyst, heat
dehydrohalogenation product(s) reagents and conditions, observations
alkene, halide ion, H2O(g), NaOH in ethanol, heat under reflux
