4. a. Compound T is the major product formed in the reaction of compounds Rand S as shown below: NaOEI (excess. EIOH 6) H,09 CHO, R . C,H,O, oli Draw the structure of compounds Rand S. 13 marks) (ii) Draw and discuss in detail the reaction mechanism for the formation of compound T from starting materials and S. What is the name of this type of reaction? [12 marks] b. (1) [3 marks) Explain what is meant by a 'cycloaddition reaction in pericyclic chemistry Predict a possible product of the following cycloaddition reaction and draw a mechanism for the reaction using curly arrows 15 marks) hv U Y di