Olivia22
Note by , created almost 6 years ago

A level Chemistry (Unit 2) Note on Chem 2.2, created by Olivia22 on 09/04/2013.

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Olivia22
Created by Olivia22 almost 6 years ago
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Page 1

AlcoholsStrong hydrogen bonds Lower volatility than alkanes of similar lengthRelatively high melting and boiling pointHydrogen bonds form between the Hydrogen of water and the lone pair of the oxygen in an alcohol. Therefore alcohols can be soluble. Solubility decreases as chain length increases-larger part of the alcohol molecule is non-polar hydrocarbon chain-hydrocarbon chain does not form hydrogen bonds with waterCombustionC2H3OH + 2O2 -> 2CO2 + 3H2O

Primary Alcohols - OH bonded with a carbon with no alkyl groups/one alkyl groupSecondary Alcohols - OH bonded with a carbon bonded to two alkyl groupsTertiary Alcohols - OH bonded with a carbon bonded to three allyl groups

OxidationPrimary Alcohols are oxidised once and distilled to produce aldehydesPrimary Alcohols are oxidised twice under reflux to produce carboxylic acidsSecondary Alcohols are oxidised to produce ketonesTertiary Alcohols cannot be oxidisedA typical oxidising agent is acidified (potassium) dichromate - turns from orange to green

EsterificationAlcohol is warmed with a carboxylic acidH2SO4 catalystEster linkage OH from carboxylic acid and H from alcohol are removed to form waternaming estersalcohol -> alkyl namecarboxylic acid -> alkanoate

Dehydration of AlcoholsConcentrated H2SO4 catalystHeatWater is produced + AlkeneElimination Reaction

Halogenoalkanes (Hga)Hydrolysis of HalogenoalkanesHga react with aqueous hot hydroxide ionsNucleophilic substitutionProduct is alcoholAs you go down Group 7 the strength of the C-Hal bond decreases (bond enthalpy decreases)  The weaker the bond enthalpy the faster the rate of hydrolysis 

CFCswere developed as aerosols,refridgerants and in air-conditioning because of low reactivity ,volatility and non-toxicityHave damaged the ozone layer

Infrared SpectroscopyAbsorption of Infrared Radiation causes covalent bonds to vibrateInfrared Spectroscopy shows the presence of bondsAlcohol - contains only C-H and O-H bondsCarboxylic acid  - contains only C-H , O-H (indicated by one peak) and C=OAldehyde/Ketone - contains only C-H and C=OModern breathalysers indicate alcohol using IR spectroscopy

Mass SpectroscopyIndicates presence of ion fragments of various massesUsed in determination of relative isotopic massA molecular ion peak is the last peak in mass spec Shows the Mr of the compound

Alcohols

Halogenoalkanes

Modern Analytical Techniques