-
Making alcohol: Fermentation
 - catalysed by an enzyme in yeast (zymase)
- 37C
- anaerobic
- concentration of 14% alcohol by volume
-
Making alcohol: Hydration of ethene
 - catalyst: phosphoric acid
- high temperature: 300C
- 60 atm
- uses steam
- 95% conversion
- unreacted gases are recycled and passed through the reactor again
-
Uses of alcohols
- Methanol: clean burning fuel, feedstock, can be converted into methanal and ethanoic acid
- Ethanol: drink, perfumes, cleaning fluids, fuel
-
Properties of alcohols
- Water solubility: hydrogen bonds form between the polar -OH groups of alcohol and water molecules
 - Volatility and boiling points: high melting and boiling points, low volatility because of hydrogen bonds
-
Primary alcohol
- -OH group attached to C bonded to no or one alkyl group

-
Secondary alcohol
- -OH group attached to a C bonded to two alkyl groups

-
Tertiary alcohol
- -OH group is attached to a C bonded to three alkyl groups

-
Combustion of alcohols
- Alcohols burn completely to form carbon dioxide and water

-
Oxidation of primary alcohols
- Distil: form an aldehyde, catalyst is acidified potassium dichromate solution (K2Cr2O7/H2SO4)
- Reflux: form a carboxylic acid, same catalyst
 - Solution turns from orange to green
-
Oxidation of secondary alcohols
- Heat: form a ketone, catalyst is acidified potassium dichromate (K2Cr2O7/H2SO4)

-
Oxidation of tertiary alcohols
- resistant to oxidation
- oxdidating agents remains orange
-
Esterifaction of alcohols
- alcohol is warmed with a carboxylic acid
- acid catalyst: usually concentrated sulfuric acid
- an ester and water is produced

-
Dehydration of an alcohol
- form an alkene
- heating under reflux
- phosphoric acid catalyst present
 
-
Halogenoalkanes
- general formula: CnH2n+1X (X is the halogen)
- fluoro- F
- chloro- Cl
- bromo- Br
- iodo- I
-
Uses of halogenoalkanes
- refridgerants
- aerosol propellants
- dry-cleaning solvents
-
Halogenoalkanes- carbon-halogen bond
- Polar: halogen atoms are more electronegative than carbon atoms, bonded electron pair is attracted more towards the halogen atom
- polarity decreases down the halogen group- electronegativity decreases
- electron-deficient carbon atom attracts nucleophiles
-
Nucleophile
electron pair donor
-
Hydrolysis of halogenoalkanes
a nucleophilic substitution reaction: a nucleophile is attracted to an electron-deficient centre or atom where it donates a pair of electrons to form a new covalent bond
-
Hydrolysis of a primary halogenoalkane
- reaction with hot aqueous acid
- the halogen atom is replaced by a hydroxide ion

-
Rates of primary halogenoalkane hydrolysis
- Polarity: C-F bond is the most polar amongst the halogenoalkanes, so the carbon atom should attract the nucleophile most readily and give the fastest reaction...
- But...
- Bond enthalpy is more important the polarity
- Bond enthalpy: C-I bond is the weakest so is broken more easily, so has a faster reaction . As the rate of raction increases, the bond enthalpy weakens

-
Experiment to show rate of hydrolysis
heating halogenoalkane with aqueous silver nitrate with ethanol added
-
Chloroethene in the production of PVC
- Uses: drainpipes, plastic window frames, sports equipment, toys, packaging
- polymerisation of chloroethene

-
Tetrafluoroethene in the production of PTFE
Uses: coating pans, nail polish- polymerisation of tetrafluoroethene
-
CFC's
- They were first developed, because refrigeration gases at the time were toxic. CFC replaced these gases as it was non-toxic and unreactive.
- CFC's remain stable until they reach the stratosphere, where hey break down in the presence of UV radiation to form chlorine radicals. These radicals catalyse the breakdown of the ozone layer
-
Percentage yield
 - Yield can be moles or mass
-
Atom economy
 - Benefits of high atom economy: reduced amount of waste products
- Addition reactions: 100% atom economy, no waste products
- Substitution reactions: waste products, less efficient
- Some reactions have a high percentage yield but low atom economy
-
Infrared spectroscopy
- absorption of infrared radiation causes covalent bond to vibrate (stretching or bending motion)
- breathalysers: measure ethnol levels by using infrared spectroscopy

-
Mass spectrometry
- Early developments: used to determine the mass-to-charge ratios of ions
- Uses: to identify unknown compounds, to determine the abundance of each isotope in an element, to gain further information abou the structure and chemical properties of molecules

-
Reaction mechanism: radical substitution
 - UV radiation provides the energy to break the covalent bond
- Bonds break by homolytic fission
-
Reaction mechanism: electrophilic addition
-
Reaction mechanism: nucleophilic substitution
|
|