chemistry topic 10/20

i hate organic chemistry

alkane to halogenoalkane

free radical substitution

* initiation
* propagation
* termination

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bromine water is decolourised

alkene to alkane

hydrogenation

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alkene + H2 → alkane using Ni catalyst at 150ºC

margarine is made this way

halogenoalkane to alkene

elimination

alkene to halogenoalkane

electrophilic addition

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has major and minor pathways

alkene to poly(alkene)

addition polymerisation

halogenolkane to alcohol

nucleophilic substitution reactions

alkene to alcohol

hydration

heat with steam and catalyst of concentrated sulphuric acid

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alkene + H2So4 → intermediate and water → alcohol

alcohol and carboxylic acid

esterification - produces an ester and water.

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carboxylic acid is the second part of the name. concentrated sulphuric acid is used as a catalyst. esters are used for flavouring, perfumes, cosmetics.

alcohol to ketone

oxidation of a secondary alcohol

alcohol to aldehyde

oxidation of a primary alcohol using distillation (aldehyde bp is lower than alcohol and carboxylic acid.

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use acidified dichromate (Kr2Cr2O7) or potassium manganate as an oxidising agent, and H2SO4 as a catalyst.

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acidified dichromate will change from orange to green

alcohol to carboxylic acid

oxidation of primary alcohol using reflux

boiling point of functional groups

**highest - because highest intermolecular forces**

carboxylic acid

alcohol

amine

ketone

aldehyde

halogenoalkane

alkane

factors determining rate of sN1 and 2

tertiary > secondary > primary (slowest)

(electronegative) F > Cl > Br > I (least electronegative, weakest bond, reacts fastest)

protic solvent = faster

electrophilic substitution

benzene + nitronium ion → nitrobenzene + hydrogen ion

primary compound

C is attached to the functional group and at least 2 H atoms

evidence for delocalised ring of electrons in Benzene

1. equal bond lengths, so can’t be double and single
2. benzene is reluctant to undergo addition, unlike alkenes, because it disrupts the ring of electrons
3. benzene is more stable, delocalisation minimizes repulsion
4. only one isomer exists

incomplete combustion

will produce either CO2 and H2O

or C and H2O

hydrogenation

alkene to alkane

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alkene + H2 → alkane using Ni catalyst at 150ºC

margarine is made this way

addition of halogen halides

alkene + hydrogen halides → halogenoalkanes

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eg. ethene + HCl → halogenoalkane

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turns bromine water from brown to colourless

reduction reactions

reversing oxidation

reducing agents:


1. sodium borohydride NaBH4
2. lithium aluminium hydride LiAlH4 - must be used to reduce carboxylic acid

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both produce hydride ion H-, which acts as a nucleophile.

characteristics of a homologous series

* successive members differ by CH2
* same general formula across members
* members show gradation in physical properties
* similar chemical properties

elimination

halogenoalkane to alkene

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halogenoalkane + KOH → alkene + KBR + H2O

reducing agents

sodium borohydride NaBH4

lithium aluminium hydride LiAlH4 - for carboxylic acids