Chemistry F324 Notes

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  • Created on: 03-01-13 19:44
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F324 Notes
Module 1
Benzene and its reactions
Nitration:
START: HNO3 + H2SO4 NO2++ H2SO4- + H2O
END: H+ + HSO4- H2SO4
Halogenation:
START: Br2 +AlBr3 Br+ + AlBr4-
END: H+ + AlBr4- AlBr3- + HBr
Carbonyls
Contain C=O bond: Aldehydes and Ketones
They have a dipole since O is more electronegative than C
Oxidation of alcohols and aldehydes
PRIMARY alcohols oxidised to aldehydes (distil) and ketones (reflux, acidified
potassium dichromate VI)
SECONDARY alcohols oxidised to ketones
Reactions of aldehydes and ketones
REDUCTION of aldehydes:
Reduced to PRIMARY alcohols
REDUCTION of ketones:
Reduced to SECONDARY alcohols
Aldehydes and ketones react with NaBH4 by nucleophilic substitution (so, the
H- with a lone pair of electrons reacts).
Carbonyl compounds chemical tests
Aldehydes + Ketone use 2,4 dinitrophenyhydrazine and yellow-orange
precipitate forms
Aldehydes use Tollen's reagent and it oxidises it to a carboxylic acid to form a
silver mirror.
To identify the carbonyl compound:
1) Yellow-orange precipitate from 2,4 DNP filtered and re crystallised and
dry it
2) Measure melting point
3) Compare it to a database
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Carboxylic acids
Between 1 and 4 Carbons are very soluble in water due to highly polar C=O and
O-H bonds which allow it to form hydrogen bonds.…read more

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During manufacture, double bonds may be removed to make the products more
solid: eg margarine. This means that the remaining double bonds are
structurally altered, so trans fats are formed.
Trans fatty acids behave like saturated fats in the body and raise LDLs (carry
cholesterol to artery walls for deposition= BAD) in the body so raise risks of
heart disease, and lower HDLs (transport cholesterol out of the blood and body
= GOOD).…read more

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Preparation of aromatic amines:
Reduce nitrobenzene or any other nitroarene using a mixture of conc HCl
under reflux. Then neutralize excess HCl.
Synthesis of dyes from phenylamine:
1) Diazotisation
It's responsible for forming the diazonium ion.…read more

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Module 2
Amino acids
General formula of an alpha amino acid: RCH(NH2)COOH
Isoelectric point: the pH value at which the amino acid exists as a zwitterion.
The isoelectric point of an amino acid depends on the R group.
The NH2 part acts as the base, so accepts protons.
The COOH part acts as the acid to donates protons.
If pH is more acidic than the isoelectric point: Amino acid behaves as a base and
ACCEPTS a PROTON FROM THE ACID, forming a POSITIVELY CHARGED ION.…read more

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Optical isomers are non-superimposable mirror images about an organic chiral
Centre.
Optical isomerism and E/Z isomers are types of stereoisomerism .
Optical isomers ROTATE PLANE POLARISED LIGHT DIFERENTLY (one rotates it
clockwise, and the other anticlockwise).
A mixture of both is known as a RACEMIC MIXTURE and it has NO EFFECT ON
PLANE POLARISED LIGHT AS THE ROTATIONS CANCEL EACH OTHER OUT.
Naturally occurring alpha amino acids are optically active (apart from glycine
which has 2 H's on the central C.…read more

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Addition and condensation polymerisation
ALKENES UNDERGO ADDITION POLYMERISATION to produce SSATURATED
CHAINS containing NO DOUBLE BONDS.
They're made from 1 type of monomer only and there is NO ADDITIONAL
PRODUCT FORMED.
Products: POLY(ALKENE)
CONDENSATION POLYMERISATION involves the elimination of a small molecule
such as H2O or HCl.…read more

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Alternatively, carbonyl bonds can be incorporated within the backbone of the
polymer which absorb light and break. They're then converted to carbon
dioxide and water in the presence of bacteria.…read more

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Module 3
Separation by chromatography
How it works:
MOBILE PHASE sweeps a mixture over a STATIONARY PHASE
-Stationary phase is fixed in place
-Mobile phase moves in a definite direction
Stationary phase intracts with the components in the mixture, slowing them
down (greater the interaction, the more it is slowed down). This means that
different components flow over the stationary phase at different speeds,
separating the components.…read more

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Limitations:
- Similar compounds often have similar Rf values
- Unknown compounds have reference Rf for comparison
- It can be difficult to separate all components in a mixture
Gas chromatography
Used to separate volatile components in a mixture.
Useful for organic compounds with a low boiling point.
RETENTION TIME is the time for a component to pass from the column inlet to
detector. Different compounds have different retention times.…read more

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