0.6 Aldol condensation  (Page 3/4)

Exercise 1 Enter the letter of any compound that does not meet the structural requirements for the aldol condensation:

Answer: C, F etc……. (Convince yourself)

Exercise 2 Write the letter of any $\beta$ -hydroxyaldehyde or $\beta$ - hydroxyketone?

Answer: B, D etc…….. (Convince yourself)

Exercise 3 Each of the following compounds was prepared by an aldol condensation followed by dehydration. In each case, select the structure of the starting material from the list of choices in the box below.

Answer: (a) FF (b) BB (c) __? __ (Convince yourself)

Exercise 4 Each of the following compounds was prepared by a crossed aldol condensation followed by dehydration. In each case, select the structures of the starting materials from the list of choices in the box above. Enter the letter of the compound that serves as the nucleophilic component followed by that of the electrophilic component. For example, the nucleophilic component used to prepare the first compound is A, while the electrophilic component is F.

Answers: (a) AF (b)

Pre-lab 2: aldol condensation (total 10 points)

Click here for the Pre-Lab

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

This assignment must be completed individually and turned in to your TA at the beginning of lab. You will not be allowed to begin the lab until you have completed this assignment.

1) Is this reaction acid or base catalyzed? Why do you need to use 1.0 M HCl at the end of the experiment? (2 points)

2) What is the role of p-nitro group in 4-nitrobenzaldehyde during the ALDOL reaction? What do you think would happen to the yield of the product if p-methoxy group was present instead of p-nitro group? (2 points)

3) Benzaldehyde (PhCHO) cannot undergo“ALDOL”reaction by itself in presence of strong base (KOH)-Why? (1 point)

4) Write the major product of the following reactions, if there is no product specifies it. (1+2+2 = 5 points)

Grading

You will be assessed on:

• Completion of Pre lab questions.
• Write-up in your Lab Notebook (see Appendix:1 Lab Notebook Guidelines )
• Completion of Report questions.
• TA evaluation of lab procedure.

Materials required

Equipment Chemicals

• Water Bath 4-nitrobenzaldehyde
• Stir bar Acetophenone
• Round bottom flask (10mL) Sodium hydroxide
• Funnel HCl (1.0 M)
• Beaker Ethanol
• Glass rod (for recrystalization) Filter paper

Safety

Wear gloves all the time, especially when working with NaOH and HCl. Keep safety glasses at all the times.

Experimental procedure

You will be assigned either procedure A (traditional experiment procedures) or procedure B (green chemistry experiment procedures). Comparison of two methods: Give percent yield and melting point temperatures to the TA so that they can be written on the board and you can then collect everyones’data.

A. traditional experiment procedure

Pre-heat your water bath to 60-70°C.

• Place a stir bar and 0.4 g of 4-nitrobenzaldehyde, 0.3 g of acetophenone and 0.10 g of sodium hydroxide in a 10 mL round bottom flask. NOTE: Acetophenone is a liquid with a density of 1.03 g/mL. Add 3.5 mL of 95% ethanol and heat the reaction mixture to 60-70°C while stirring for 20 minutes. Do not overheat your product otherwise you will polymerize your sample.