Aldol condensation drawing

PROBLEMS Now let s get some practice drawing mechanisms for aldol condensations. Draw a mechanism for each of the following transformations. You wiU need a separate piece of paper to record each of your answers ... 

Problem 23,4 Aldol condensation of 3-methylcyclohexanone leads to a mixture of two enone products, not counting double-bond isomers. Draw them. 

The sequence of cyclohexene cleavage and aldol reaction on the dicarbonyl product gives ring-contracted cyclopentenes. This proved particularly valuable when Iwata6 wanted to make subergorgic acid 41 that has three five-membered rings awkwardly joined around a quaternary carbon atom. So crowded are these compounds that they are difficult to draw clearly. Ozono-lysis of the synthetic cyclohexene 38 gave the unstable dialdehyde 39 that cyclised by an aldol condensation to 40 and hence could be oxidised to 41. 

Draw a mechanism for this reaction (show electron-pushing arrows). (Hint Take another look at aldol condensations, then consider the name of this enzyme.)... 

The general principles for proposing reaction mechanisms, first introduced in Chapter 4 and summarized in Appendix 3 A, are applied here to a crossed aldol condensation. This example emphasizes a base-catalyzed reaction involving strong nucleophiles. In drawing mechanisms, be careful to draw all the bonds and substituents of each carbon atom involved. Show each step separately, and draw curved arrows to show the movement of electrons from the nucleophile to the electrophile. 

It is not difficult to predict the products of the Robinson annulation and to draw the mechanisms if you remember that the Michael addition is first, followed by an aldol condensation with dehydration to give a cyclohexenone. 

The first reactions are an aldol condensation and a conjugate addition. We have shown just the first steps, but make sure that you can draw full mechanisms for both. The last step is a standard pyridine synthesis. 

Draw the structure of all aldol condensation products for each of the following reactions ... 

One way to draw the product is to draw the entire mechanism, but for aldol condensations, there is a faster method for drawing the product. Begin by identifying the a protons ... 

Draw the product obtained when each of the following compounds is heated in the presence of a base to give an aldol condensation. 

EXERCISE 7.37 Draw the aldol condensation prodnct that is obtained when the following compound is heated in the presence of hydroxide ions ... 

The intramolecular aldol condensation of 2-(3-oxobutyl)cyclohexanone (margin) can, in principle, lead to four different compounds (ignoring stereochemistry). Draw them and suggest which one would be the most likely to form. (Hint Build models )... 

Draw the structure of the dicarbonyl compound required for synthesis of each of the following products by an aldol condensation. 

DRAW THE PRODUCT OF THE ALDOL CONDENSATION REACTION THAT OCCURS WHEN THE FOLLOWING COMPOUND IS HEATED WITH SODIUM HYDROXIDE ... 

A Robinson annulation is comprised of a Michael reaction, followed by an intramolecular aldol condensation. To determine the starting materials necessary to prepare the desired product via a Robinson annulation, we draw the following retro synthetic analysis ... 

Now that we have identified which carbon-carbon bond will be formed during an intramolecular aldol condensation, we can draw the product by removing the following two highlighted a protons and the oxygen atom, and we replace them with a double bond, giving a product with the molecular formula C12H12O ... 

Thomson -JOnV Click Organic Interactive to learn to draw the structures of products from aldol-type condensation reactions. 

Predict the products of aldol, Claisen, and Michael condensations, and draw mechanisms to show how they are formed. Show how these condensations are useful in synthesis. 

Problem 2.3. An aldol reaction is one of the key steps in the benzoin condensation, which requires a catalytic amount of CN to proceed. Draw a reasonable mechanism. 

Drawing mechanisms for the simplest of aldols self-condensation of aldehydes and ketones. 

The trouble is that it is too reactive. It tends to react more than once and to give extra unwanted reactions as well. You might think that condensation between acetaldehyde and formaldehyde in base would be quite simple. The acetaldehyde alone can form an enolate, and this enolate will attack the more electrophilic carbonyl group, which is formaldehyde. In each reaction the only possible enolate attacks another molecule of formaldehyde. By now you have got the idea so we simply draw the next enolate and the structure of the third aldol. 

Draw the aldol sequence for self-condensation of 3-pentanone with sodium ethoxide (NaOEt) in ethanol. 

Draw the aldol product formed by self-condensation of 27 and 2. 

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