Draw the intermediate in the following reaction.

Draw the structures of the hemiacetals or hemiketals formed in these reactions: 

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Cyclic hemiacetals commonly form if a molecule has both an alcohol group and a carbonyl group elsewhere in the same molecule, especially if they are four or five carbons apart. What is the structure of the hydroxy aldehyde from which this hemiacetal might form? 

<IMAGE> Cyclic hemiacetal

In Problem 15.24, you were given the structure of the free aldehyde form of glucose. Try to draw the two cyclic hemiacetal forms of glucose you would get if (a) the OH on C4 formed the ring and (b) the OH on C3 formed the ring.

What would be the product of the following reaction?

Draw the structure of the product when one mole of cyclopentanone reacts with two moles of methanol in an acidic solution.

Determine whether the following compounds are acetals or ketals. Draw the structure of the aldehyde or ketone it came from.

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Draw the structures of the hemiacetals or hemiketals formed in these reactions: 

b. <IMAGE>