functional group cehmistry

<3

free-radical substitution: which homologous series + mechanism

alkanes --> halogenoalkanes
1. initiation - creation of free radicals in UV light
2. propagation: free-radical reacts with alkane to produce alkane radical and hydrogen halide; alkane radical reacts with halogen to form halogenoalkane and halogen free radical
3. termination: collision of all free radicals in different combinations

organic synthesis of methane reaction

Al4C3 + HCl --> 4AlCl3 +3CH4
aluminum carbide

synthesis of other alkanes

raction between the grignard reagent and water
R-MgX + H2O --> RMgOHX + R-H (alkane)

Why do alkanes not undergo addition reactions, but only substitution reactions?

Since all alkanes are staurated, it means they have only single sigma bonds, hence they cannot be more stable and they can only change a substituent for another one, but don't add any substituents.

addition of halogens - which homologous series + product + catalyst

alkenes, halogenoalkanes are produced, in non-polar solvents (like CCl4)
C2H4 + Br2 --> C2H4Br2

addition of water - which series + product + catalyst

alkenes, alcohols are produced, acidic conditions

addition of hydrogen halides - which series + product

alkenes --> halogenoalkanes
C4H8 + 2HBr --> C4H8Br2 + H2

hydrogenation of alkenes - product + catalyst

alkanes are produced, Ni, Pt, Pd catalysts required

hydrogenation of alkenes - application

oleic acid + H2 --> steric acid
C17H33COOH + H2 --> C17H35COOH

addition polymerisation - conditions + reactants + products

p, T conditions, monomer (alkene) is the reactant, repeating unit with a broken double bond is the product

reaction of alkenes with hydrogen peroxide - product + conditions

dihydroxyalcohols are produced, acidic conditions

how to distinguish between alkane and alkene?

Alkenes have double bonds, which will discolourate the solution of KMnO4 or Br2, alkanes will not cause observable changes (unless in UV light)

What happens if a few drops of Br2 will be put in an alkane solution in the presence of UV light?

free-radical substitution will take place, so Br2 will discolourate from dark brown/red to colourless

are alcohols volatile?

no

alcohols dissolve in...

both polar and non-polar solvents

solubility of alcohols

greater for alcohols of shorter chains

boiling point

increases for longer chains

preparation of alcohols - 2 methods

1. alkenes + water
2. halogenoalkanes with alkalis --> nucleophilic substitution

nucleophilic substitution: alkyl halides and alkalis

C3H7Br + OH- --> C3H7OH + Br-
temperature required!!

esterification

condensation between alcohols and carboxylic acids, concentrated H2SO4 required

reaction between alcohols and active metals

H is taken away from the OH group and it is exchanged for the metal, so a salt is produced and H2

do alcohols undergo combustion?

yes of course; if it is incomplete it will burn with a very smoky flame

oxidation mixture for alcohols

K2Cr2O7, H+, T

do tertiary alcohols undergo oxidation?

no

what are secondary alcohols oxidised to?

ketones

what are primary alcohols oxidised to?

1. after distillation -->aldehydes
2. after reflux --> carboxylic acids