Chemistry: Structural Differences and Formulae

Questions 1:
a) Why do alkanes react only by homolysis?
b) What happens with nucleophilic substitution of bromoethane with sodium hydroxide?
Explain the following terms: Addition reaction, homolysis and heterolysis, and nucleophile and electrophile.

Question 2:
What are the structural formulae of compounds A-H? Explain your reasoning. There are four compounds, A-D, all with molecular formula C4H8. Compound A is a cis-isomer and compound B is a trans-isomer. Both react with concentrated sulphuric acid, followed by water to yield a compound E of formula C4H10O. Compound C reacts with sulphuric acid followed by water, to yield mostly compound E, but also some compound F, also C4H10O. Compound D also reacts reacts with sulphuric acid and water to produce a major product G and a minor product H, both of formula C4H10O also.

Question 3:
Explain the difference in structure between a primary, secondary and tertiary alcohol (Alkanol). Outline, with equations, the product(s) of oxidation of each of the above three types of alcohol.

Question 4:
You are provided with a mixture which you suspect may consist of hexane, hexylamine and propanol.
a) How would you attempt to separate the mixture?
b) Suggest a chemical or physical test, which would help to confirm your suspicion as to the chemical nature of each of the three components?

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...pens with polar molecules
- happens with molecules constructed from atoms of
dissimilar electronegativity.

When a molecule is formed by atoms with dissimilar electronegativity, electrons involved in the chemical bond tend to stay most probably near the nucleus of the most electronegative atom. This causes a little negative charge on the most electronegative atom and a little positive charge on the least electronegative atom. Groups that attack the positively charged atom are called "nucleophilic".

Groups that attack the atoms with external non bonded electron pairs or other atoms with a small negative charge are called electrophilic.

a) Alkanes are formed exclusively by carbon and hydrogen atoms, they are non polar molecules. Since heterolysis happens in polar molecules, formed by atoms of dissimilar electronegativity, only homolysis is possible in this case.

b) Bromoethane with sodium hydroxide
CH3 CH Br + Na++:OH- -> CH3 CH OH + Na++Br-
C carbon with delta + charge, : nucleophilic electron pair

Question 2:
Since the formula of compounds A-D is CnH2n type, these compounds are alkenes. There is only one way to dispose the double bound so as to have cys and trans isomers. So ...