A2 Chemistry Revision Notes

A2 Chemistry Revision Notes

An arene is an aromatic hydrocarbon

An RF value is the distance travelled by the solute divided by the distance travelled by the solvent front.

Retention time is the time between injection and emergence

Aldehyde + NaBH4  Alcohol

A stereoisomer is a molecule with the same structural formula but different special arrangement.

Delocalized pi electrons are electrons spread over more then two atoms where the p orbital overlap sideways

The molecular ion peak is the peak caused by the unfragmented molecule

A base peak is the peak with the greatest relative intensity; it represents the most abundant fragment

A Zwitter ion is a molecule with both a + and – charges

The conditions for esterification are conc H2SO4 and reflux

The nitration of benzene is important in the pharmaceutical and dye industries

A curly arrow represents the movement of a pair of electrons to form or break a covalent bond

To make an azo dye you first have to react an aromatic amine with HNO2 and HCl at a temperature below 10oc, this forms a dizonium salt. This then undergoes a coupling reaction with phenol in alkali conditions.

To make Tolens reagent you mix silver nitrate and ammonia

Hydrolysis is the splitting of a compound with a reaction with a water molecule

To get a pure stereoisomer use a stereo specific chiral catalyst

Primary amines can act as bases because the loan pair of electrons on the N can be donated to a H+ to form a dative covalent bond

The evidence that led scientists to doubt the model proposal by kekule are all C-C are the same length, the ∆ H of hydrogenation is less exothermic then expected and benzene only reacts with a halogen at high temp or in the presence of a halogen carrier

An alpha amino acid is an amino acid with both the NH2 and the COOH on the same carbon

Thin layer chromatography works on the basis that the compounds adsorbing to the stationary phase.

Radio waves is the region of the electromagnetic spectrum that is used for NMR spectroscopy

Phenol and cyclohexane both react more readily with halogens compound compared with benzene. This is because in benzene the pi electrons are delocalised over the ring, however in phenol the loan pair from the O are delocalised into the ring therefore increasing has a higher electron density then benzene. In cyclohexane the pi electrons are localised between two carbons so also has a higher electron density then benzene. Because cyclohexane and phenol have a higher electron density they can induce a dipole on the halogen molecule whereas benzene can’t induce a dipole on the halogen molecule

Polyester can be readily hydrolysed by hot alkali and acid

Polymers with a C=O are more likely to be degradable then polymers with only single bonds because the double bonds absorb radiation and the double bond breaks

A halogen carrier allows benzene to be halogenated by inducing a permanent dipole on the halogen molecule

If a silver mirror is formed when carrying out the Tolens reagent test the compound tested was an aldehyde

The Ag+ is reduced to a Ag and the aldehyde is oxidised to a carboxylic acid when the Tolens reagent test is carried out on an aldehyde

To distinguish between compounds using precipitates you would recrystalise the precipitate to purify it then measure the melting point of the purified precipitate and compare to know values.

The general formula for an amino acid is RCH(NH2)COOH

TMS gives a peak at 0 in NMR

SO4 has a charge of 2-

Benzene goes through substitution because it maintains the stability of the molecule

If K were added to liquid phenol you would observe effervescence and the K would disappear

Phenol is used in the production of azo dyes, pharmaceuticals and cleaning agents and detergents

A shorthand notation for fatty acids consists of two numbers separated by a colon. The first one represents the number of carbons and the second represents the number of double bonds. If there are any double bonds numbers in brackets will follow to indicate on what carbons the double bonds occur. Example:

CH3CHCHCH2CHCHCH2CH2CHCHCH2COOH

12:3 (2,5,9)

A simple triglyceride is when the three fatty acids connected to the triol are the same. A mixed triglyceride is when the three fatty acids are different

Trans – hex – 3 – ene

Cis – hex – 3 – ene

NO3 has a charge of -1

NO2+ is called a nitronium ion

Tetrahydridoborate is NaBH4

CH3CH2CH2NH3+Cl- is called popyleammonium chloride

When turning a normal amino acid into a Zwitter ion the functional groups on the R group don’t change

Acid Hydrolysis is always HCl

Examples of polyesters are Terylene and Poly (lactic acid)

Examples of polyamides are Kevlar and Nylon – 6,6

A mobile phase is a phase that moves

A stationary phase is a phase that does not move

A solid stationary phase separates the components by adsorption.

A liquid stationary phase separates the components by relative solubility. Different components have different solubility’s

The stationary phase in the TLC is Silica gel on an inert solid support and the mobile phase is a liquid solvent.

In gas chromatography the stationary phase is a liquid or a inert solid support. The mobile phase is the gas

GCMS is used in drug detection, environmental analysis, airport security and space probes.

Deutered solvents are used because they do not give a signal in proton NMR. CDCl3 is an example.

D2O is used to exchange with protons in OH and NH; this aids the identification of OH and NH protons

Reasons for not getting 100% yield are: side reactions occur, loss into atmosphere, not all reactants react and mechanical loss. General formula

Compound

CnH2n+2

Alkane

CnH2n

Alkene

CnH2n+2O

Alcohol

CnH2nO

Aldehyde / Ketone

CnH2nO2

Carboxylic acid / Ester

CnH2n-6

Benzene compound

Moles Density Volume

HCl + NaNO2  HNO2 + NaCl

+ NO2

+ HCl

CH3Cl



+ HNO3  jl;k + H2O

Conditions :conc H2SO4, conc HNO3, reflux and temperature 50oc

+ Cl

Cl2  + HCl

Conditions : FeCl3

OH NaOH  O-Na+ + H2O

+

NO2

+ 6[H]

NH2 + 2 H2O



Conditions : Sn, HCl, reflux

Carbonyl

+

[H]

Alcohol



Conditions: NaBH4, reflux

Ketone

+ 2,4 – DNPH



Orange Precipitate

Cl2

+

FeCl3



Cl+

+

FeCl4-

H+

+

FeCl4-



FeCl3 +

CH3CH2CH2COOH + CO2 + H2O

+

MgCO3

HCl



(CH3CH2CH2COO-)2Mg2+

Acid hydrolysis CH3CH2CH2CH2CH2CH2OOCCH2CH2CH3 + H2O  CH3CH2CH2CH2CH2CH2OH + CH3CH2CH2COOH Conditions: HCl

, reflux

(aq)

Alkali hydrolysis CH3CH2CH2CH2CH2CH2OOCCH2CH2CH3 + NaOH  CH3CH2CH2CH2CH2CH2OH + CH3CH2CH2COO-Na+

Conditions: NaOH

CH3CH2CH2CH2NH2

(aq)

, reflux

+

HNO3



CH3CH2CH2CH2NH3+NO3-

CH3CH2CH2CH2NH2

+

Halogeno alkane NH4+Halogen-

+

CHl



CH3CH2CH2CH2NH3+Cl–

2NH3



Amine

2[O]



CH3CH2CH2COOH

+

Conditions: Ethanol

CH3CH2CH2CH2OH H2O

+

+

Conditions: K2Cr2O7, H2SO4, relfux

CH3CH2CH2CH2OH

+

[O]

CH3CH2CH2CHO



+ H2 O

Conditions: K2Cr2O7, H2SO4, distil

CH3COHCH2CH3

+

[O]



CH3CHOCH2CH3 + H2O

Conditions: K2Cr2O7, H2SO4, reflux

HNO3 C6H6 H+

+ H2SO4 +

+

NO2+ HSO4-



C6H5NO2

 

CH3CH(NH3+)COOH2O

NO2+

+

HSO4-

+

H2 O

+ H+

H2SO4

+

NaOH

 CH3CH(NH2)COO-Na+

+

2 OH 2 Na  2 OH-Na+ + H2

+