Chemistry
ghazi4
CH4202andCH7002ContinousAssessmentDrDoveston1.pdf
CH4202 and CH7002 Retrosynthesis Continuous Assessment Exercise
Deadline: Friday 13th December, 17.00.
The exercise must be completed individually. It must be submitted as a single pdf document via the Turnitin link on Blackboard under the Assessment and Feedback tab. It must be legible. You can either work by hand (and scan the document in for submission) or use ChemDraw. ChemDraw is likely to be very useful in part B. It is important that curly arrows and structures are drawn accurately. There will be a chance to get some support in the Workshop held in November and a subsequent drop in session. You can contact me by email at any time. Part One 1. The proportions of enol in a neat sample of the two ketones below are shown. Why are they so
different? Use the term pKa and a mechanism to explain your answer.
[3 marks]
2. Suggest how the following compounds might be made by the alkylation of an enol or enolate. Your answer should include a retrosynthetic analysis, a proposed forward synthesis and brief mechanisms.
[3 marks]
3. Suggest how the following molecule can be made using the following approaches. Your answer should include a retrosynthetic analysis, a proposed forward synthesis and brief mechanisms.
(i) Dithiane chemistry. [3 marks] (ii) An acetylene anion. [3 marks]
4. Suggest a synthetic route for preparing the following 1,4-diketone using enamine chemistry. Your answer should include a retrosynthetic analysis, a proposed forward synthesis and full mechanisms.
[4 marks]
Part 2 Carry out a retrosynthesis on compound (A). Suggest a forward synthesis using (B) as one of the starting materials. You do not need to provide any mechanisms.
[24 marks]
Note: Part 2 will likely take some time. There are a number of possible solutions but all draw on chemistry that you have met in the last 4 lectures or in the past. Constructing your answer will require consultation of text books, the literature (SciFinder, Reaxys) and the course notes in order to identify suitable synthetic transformations. Include any references you use in the style of your MChem or MSc report. You do not need to reference your notes. Hint: start by disconnecting the hemi-acetal. Marking Criteria: Marks will be awarded for any logical disconnection or forward reaction. As a guide, the breakdown of marks awarded will be as follows. A logical and well-presented retrosynthetic analysis – 9 marks. A logical and well-presented forward synthesis route – 9 marks. Use of references and evidence of wider research beyond the course content – 5 marks.
