2.2.1 Alcohols

Properties and preparation of ethanol

H3PO4 is usually used as the acid catalyst.
Candidates should be able to:
(a) explain, in terms of hydrogen bonding, the water solubility and the relatively low volatility of alcohols;
(b) describe the industrial production of ethanol by: (i) fermentation from sugars, ie from glucose, (ii) the reaction of ethene with steam in the presence of an acid catalyst;
(c) outline, for alcohols: (i) the use of ethanol in alcoholic drinks and as a solvent in the form of methylated spirits, (ii) the use of methanol as a petrol additive
to improve combustion and its increasing importance as a feedstock in the production of organic chemicals;

Reactions of alcohols

Equations should use [O] to represent the oxidising agent.
Mechanism for elimination not required.
H3PO4 or H2SO4 is usually used as the acid catalyst.
(d) classify alcohols into primary, secondary and tertiary alcohols;
(e) describe the combustion of alcohols;
(f) describe the oxidation of alcohols using Cr2O7 2–/H+ (ie K2Cr2O7/H2SO4), including: (i) the oxidation of primary alcohols to form aldehydes and carboxylic acids; the control of the oxidation product using different reaction conditions, (ii) the oxidation of secondary alcohols to form ketones, (iii) the resistance to oxidation of tertiary alcohols;
(g) describe the esterification of alcohols with carboxylic acids in the presence of an acid catalyst;
(h) describe elimination of H2O from alcohols in the presence of an acid catalyst and heat to form alkenes.
2.2.2 Halogenoalkanes

Substitution reactions of halogenoalkanes

Aqueous silver nitrate in ethanol can be used to compare these rates. In this reaction, H2O can be assumed to be the nucleophile.
Alternatively, hot aqueous alkali can be used (followed by neutralisation and addition of aqueous silver nitrate). In this reaction, OH– is the nucleophile.
Candidates should be able to:
(a) describe the hydrolysis of halogenoalkanes as a substitution reaction;
(b) define the term nucleophile as an electron pair donor;
(c) describe the mechanism of nucleophilic substitution in the hydrolysis of primary halogenoalkanes with hot aqueous alkali

(d) explain the rates of hydrolysis of primary halogenoalkanes in terms of the relative bond enthalpies of carbon–halogen bonds (C–F, C–Cl, C–Br and C–I);

Uses of halogenoalkanes

Initial use of CFCs as harmless aerosol
propellants offset when scientists discovered that CFCs damaged the ozone layer.
This provided important evidence which
enabled international action to be taken to reduce and phase out CFC use.
This has subsequently led to development of ozone-friendly alternatives and natural repair of the ozone layer.

(e) outline the uses of chloroethene and tetrafluoroethene to produce the plastics PVC and PTFE

(f) explain that CFCs: (i) were developed as aerosols, refrigerants, and in air-conditioning because of their low reactivity, volatility and non-toxicity, (ii) have caused environmental damage to
the ozone layer (see also 2.4.1.g);
(g) outline the role of green chemistry in minimising damage to the environment by promoting biodegradable alternatives to CFCs, such as hydrocarbons and HCFCs; CO2 as a blowing agent for expanded polymers.
2.2.3 Modern Analytical Techniques

Infrared spectroscopy

In examinations, infrared absorption data will be provided on the Data Sheet.
Candidates should be aware that most organic compounds produce a peak at approximately 3000 cm–1 due to absorption by C–H bonds.
Use of analytical techniques to inform decision
making, ie breathalysers in drink driving cases.
Candidates should be able to:
(a) state that absorption of infrared radiation causes covalent bonds to vibrate;
(b) identify, using an infrared spectrum of an organic compound: (i) an alcohol from an absorption peak of the O–H bond, (ii) an aldehyde or ketone from an absorption peak of the C=O bond, (iii) a carboxylic acid from an absorption peak of the C=O bond and a broad absorption peak of the OH bond;
(c) state that modern breathalysers measure ethanol in the breath by analysis using infrared spectroscopy;

Mass spectrometry

Is there life on Mars?, how much
lead/pesticides enters the food chain via vegetables, etc.
Knowledge of the mass spectrometer is not required.
Limited to ions with single charges.
Rearrangement reactions are not required.
Mass spectra limited to alkanes, alkenes and alcohols.
(d) outline the use of mass spectrometry: (i) in the determination of relative isotopic masses, (ii) as a method for identifying elements, ie use in the Mars space probe and in monitoring levels of environmental pollution, such as lead;
(e) interpret mass spectra of elements in terms of isotopic abundances;
(f) use the molecular ion peak in a mass spectrum of an organic molecule to determine its molecular mass;
(g) suggest the identity of the major fragment ions, ie m/z = 29 as CH3CH2+, in a given mass spectrum (limited to alkanes, alkenes and alcohols);

(h) use molecular ion peaks and fragmentation peaks to identify structures (limited to unipositive ions);
(i) explain that a mass spectrum is essentially a fingerprint for the molecule that can be identified by computer using a spectral database.

	Erstellt von gallen96 vor etwa 10 Jahre

A-Level Chemistry (F322: Module 2 - Alcohols, Halogenoalkanes and Analysis) Notiz am F322: Module 2 Specification, erstellt von gallen96 am 01/04/2014.