ATSR Summative Coursework
Instructions :
(a) Please enter your student number below, print this worksheet out and fill in the blanks by hand. * Ensure you draw structures clearly and show mechanistic arrows with precision between where they are coming from and where they are going to. Ambiguity will not receive marks.
(b) Please scan (or photograph) the completed sheet and upload them onto your section of Gradescope on Keats AS A PDF. It is your responsibility to ensure the quality of the image is good enough for us to mark. Poor quality reproductions will NOT be marked and will receive 0 marks.
(c) You should ensure that you leave plenty of time to submit to Keats by the deadline. Emailed submissions to the module lead, or any of the other teaching staff WILL NOT BE ACCEPTED.
*Unless you have special dispensation to do otherwise.
1)
(a) With reference to stereoelectronics, explain the following observation, and classify both processes according to Baldwin’s rules. You should draw orbitals to illustrate your answer
(5 marks)
(b) Although the cyclization of 1 is not possible under basic conditions, it does work under acidic conditions. Provide a mechanistic explanation for this.
(8 marks)
c) The rate of cyclization of 3 (below) is much faster than for the corresponding substrate 4 (below). Give the name for this phenomenon and a plausible explanation as to why it occurs.
(5 marks)
2) Using stereoelectronics to justify your answer, explain the observed differences in reaction rates below (Hint : You should draw 3D structures and/or Newman projections as well as the orbitals involved).
(5 marks)
3) Using the carbocation below as an example, explain what is meant by the term 1,2- shift. Within your answer, you should draw the orbitals involved in the rearrarangement and explain which of the groups is most likely to migrate.
[5 marks]
4) Using orbitals and curly arrows to illustrate your answer, explain the outcome of the following reaction.
[5 marks]
5) Treatment of the compound below with boron trifluoride etherate gives four products of which two are shown.
a) Give a mechanistic rationale for the formation of both products. [8 marks]
b) Predict the structure of ONE of the remaining two products and provide a mechanism for its formation. [5 marks]
6) Treatment of the adamantane below with acid gives a rearrangement product with formula C14 H22. Amongst the various 1 H NMR signals of this product, there are two doublets between 4.7 and 4.85, both with a J value of 1.5 Hz. Predict the structure of this product and give a mechanism for its formation. You should also rationalise any stereochemical aspect of the reaction.
[8 marks]
7) Provide a full mechanism for the formation of C. Identify all the intermediates and by-products, and clearly label the:
(i) initiation step(s)
(ii) propagation step(s)
(6 marks)
8) Provide full mechanisms for the conversions of:
(i) D→E
(ii) E→ F
(5 marks)
9) Provide a full mechanism for the formation of cyclopentanol H. Classify the ring- forming process that generates H according to Baldwin’s rules for ring closure.
(4 marks)
10) For each of the following reactions, a single stereoisomer is formed. Give mechanisms, indicating product stereochemistry, and classifying any pericyclic reactions (4 x 5 marks for mechanism and product stereochemistry, 6 marks for identification of pericyclic processes).