M4S3: Analysis & Organic synthesis

Mass spectrum

• Shows relative isotopic abundance of element to work out relative atomic mass

• Produced by mass spectrometer

• Y-axis: % abundance

• X-axis: mass/charge ratio

Mass spectrometer

Molecules are bombarded with electrons and M⁺ ions form as electrons remove electrons from molecules

Fragmentation

When molecule bombarded, some of molecular ions break up into fragments = fragment pattern of mass spectrum

Reflux

• Used to prevent reactant evaporating before react

• Mixture heated with flask fitted with vertical Liebig condenser

• Heated electrically to avoid flame

Distillation

• Separate liquids different boiling points

• Substances evaporate in order of increasing bp

• Redistillation can be used for mixtures that contain violent liquids, allowing the product and its impurities to be separated

separation

• After reaction complete, pour into separation funnel & add water and shake then allowed to settle

• Organic layer less dense than aq layer so settle at top

• Separate desired layer and add drying agent such as MgSO₄

• Redistill

Drying agents

• If use separation, organic layer contains traces of water, need to be dried

• Can add anhydrous salt e.g. MgSO₄ which binds with water = hydrated

• initially become lumps, add more, filter mixture

• Need to redistil after this

Alkane

• Functional group: only C-C & C-H

• Prefix/suffix: -ane

• Properties: Non-polar, unreactive

• Typical reactions: radical substitution

Alkene

• Functional group: C=C

• Prefix/suffix: -ene

• Properties: Non-polar, election rich double bond

• Typical reactions: electrophilic addition

Alcohol

• Functional group: C-OH

• Prefix/suffix: -ol (or hydroxy-)

• Properties: Polar C-OH bond

• Typical reactions: Nucleophilic substitution, dehydration, elimination, oxidation

Haloalkane

• Functional group: C-X

• Prefix/suffix: halo-

• Properties: Polar C-X bond

• Typical reactions: Nucleophilic substitution

Ketone

• Functional group: C=O

• Prefix/suffix: -one

• Properties: Polar C=O

• Typical reactions: N/A

Aldehyde

• Functional group: HC=O

• Prefix/suffix: -al

• Properties: Polar C=O bond

• Typical reactions: Oxidation

Carboxylic acid

• Functional group: -COOH

• Prefix/suffix: -oic acid

• Properties: Electon-defient carbon centre

• Typical reactions: N/A

IR spectroscopy

• Beam IR radiation passed through sample of chemicals, IR radiation absorbed by covalent bonds in molecules = Increase vibrational energy

• Different bonds in different places absorb different frequencies

• spectrum shows what frequencies of radiation bonds in molecules absorb

Aplications

• Breathalyser

• Monitoring pollutants