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1. Hard organometallic reagents are important in many synthetic routes, both on in research labs and on an industrial scale. The nature of the metal has a significant effect on the reactivity observed. a. With reference to the ionicity and covalency of the bonding, explain which of organo-lithium or organo-zinc reagents are considered "harder" and why. [3 marks] b. How does the reactivity of organocadmium reagents compare to that of equivalent organozinc reagents? Use this fact to explain why organocadmium reagents are not widely used. [2 marks] c. Diphenylzinc is dimeric in the solid side. Predict the degree of aggregation it will exhibit when dissolved in ) benzene and (i) THF, drawing the resultant structures. Explain your reasoning [4 marks) Salicylaldehyde reacts with diethyl zinc in a 1:1 ratio to form compound A according to the following scheme: OH O + Et Zn A + gas On cooling, compound B crystallises from solution, and half an equivalent of diethyl zinc is found to have reformed in solution. A B + 0.5 Et Zn d. Identify A, B, and the gas.

e. By what process does A transform to B? Sketch a plausible intermediate. [2 marks] f. A reacts cleanly with anhydrous HCl to release a gas and form compound C. Identify C, and explain why this is the sole product. [2 marks] Question continues on next page g. A reacts cleanly with MezSiCl to form compound D, with molecular weight 194, a colourless crystalline solid, E, and reform some Et Zn. Identify D and E using the available data, and explain why this is the sole product. [4 marks)