Organic Chemistry

• Identify the longest carbon chain (meth-, eth-, prop-, but-) • Identify the type of bonding (sing. -an-, dbl. -en-, trp. -yn-) • Identify the functional group (hydrogen -e, hydroxyl -ol, amino- , chloro- …) • Numbers are used to give the position of groups or bonds along the chain.

Hydrogen (-e) Hydroxyl (-ol) Amino (amino-) Aldehyde (-al) Ketone (-one) Carboxyl (-oic acid) Ester (-oate)

If one = hydrogen atom is removed from an alkane what is left is known as an alkyl radical. eg. ethyl C2H5

Homologous series have the same general formula with the neighbouring members of the series differing by -CH2- The chemical properties of the individual members of a homologous series are similar and they show a gradual change in physical properties.

Ester - (-COOR) -Anoate -Methyl propanoate CnH2n+1COOH

-OH -anol Ethanol CnH2n+1OH

R-O-R’ -anal Propanal R-CHO

RCR’O -anona propanone R-CO-R’

COOH -anoic acid propanoic aciid CnH2n+1COOH

-NH2 -anamine ethanamine —

CN -anenitrile propaneniitrile —

C6H5 -benzene methyl benzene —

primary - one R group Secondary - two R groups tertiary - Three R groups

When branching occurs the molecules become more spherical in shape, which reduces the contact surface area between them and lowers the boiling point.

increased length reduces solubulity

Alkanes can react with chlorine (or other halogens) in the presence o ultraviolet light to orm hydrogen chloride and a substituted alkane, e.g. methane can react with chlorine to orm chloromethane and ethane can react with bromine to orm bromoethane.

In heterolytic fssion both o the shared electrons go to one o the atoms resulting in a negative and a positive ion. In homolytic fssion each o the two atoms orming the bond retains one o the shared electrons resulting in the ormation o two free radicals

The bond between two halogen atoms is weaker than the CH or CC bond in methane and can break homolytically in the presence o ultraviolet light. This stage o the mechanism is called initiation. Free radicals contain an unpaired electron and are highly reactive. When the chlorine ree radicals come into contact with a methane molecule they combine with a hydrogen atom to produce hydrogen chloride and a methyl radical. Since a new radical is produced this stage o the mechanism is called propagation. The methyl ree radical is also extremely reactive and reacts with a chlorine molecule to orm the product and regenerate another chlorine radical. This is a urther propagation step and enables a chain reaction to occur as the process can repeat itsel. In theory a single chlorine radical may cause up to 10 000 molecules o chloromethane to be ormed. Termination occurs when two radicals react together.

Always an Alkene + Water (conc H2SO4 cat.) or Bromine or Hydrogen or Hydrogen halide

An alkane

An alcohol if conc. H2SO4 is used as a catalyst

Halogenoalkane

Dihalogenoalkane

Ethanol can be readily oxidized by warming with an acidied solution o potassium dichromate(VI). During the process the orange dichromate(VI) ion Cr O 2 - is reduced rom an oxidation state o +6 to the green Cr3 + ion The product of this is ethanal which is very volitle due its lack of hydrogen bonding. If the aldehyde is sufficent than the ethanal can be distilled. If further oxidation is required than the reactioon should continue in a reflux where the ethanal is oxidised to ethanoic acid.`