AS and A2 Chemistry notes and resources (WJEC specification) - UNIT CH2. Properties, Structure and Bonding

The uses to which materials can be put depend on their properties, which in turn depend on the bonding and structure within the material. By understanding the relationship between these factors, chemists are able to design new materials. The types of forces that can exist between particles are studied, along with several types of solid structures, in order to illustrate how these factors influence properties. The building blocks of materials are the elements and the relationship of their properties to their position in the Periodic Table is illustrated by a study of the elements of the s-block and Group 7. An introduction to organic chemistry provides the basis for an understanding of how the properties of carbon compounds can be modified by the introduction of functional groups.

7.2 - Hydrocarbons

Candidates should be able to:

(a) understand and explain the meaning of the terms homolytic and heterolytic bond fission;

(b) describe in outline the general nature of petroleum, its separation into useful fractions by fractional distillation, and the cracking process;

(c)

(d) describe the structure of and bonding in ethene (hybridisation is not appropriate here);

(e) classify the addition reactions of Br2 and HBr (involving heterolytic fission), with ethene and propene, and relate the orientation of the normal addition of HBr to propene to the recalled mechanism of the reaction and the relative stabilities of the possible carbocations (carbonium ions) involved;

(f) recall the catalytic hydrogenation (reduction) of alkenes and the preparation of ethene by elimination of HBr from bromoethane ¢Ó;

(g) understand the nature of alkene polymerisation and show an awareness of the wide range of important polymers of alkenes and substituted alkenes.