[chmstud101]

I'm having a tough time finding the mechanism for the following reaction.  I have also included my attempt at it.  I'm not really sure if I am on the right track or not.  I know I could make one of the OH groups into a leaving group as water but I don't know if that would help or not.  Any help would be greatly appreciated.

[orgopete]

You have virtually everything you need to answer this question. Let me point out what you have done. In your proposed mechanism, structures 2 and 3 are in equilibrium. The ring can form and break. If you replace the carboxylic acid OH with a hydrogen, you could write the same mechanism. You might even find it useful to replace the ring in 1 with a CH₂OH group, and draw two mechanisms with these modified structures. You will need to complete formation of a double bond by the loss of water.

If you do that, you might recognize that a CH₂OH group is attached to a five carbon chain between a carboxylic acid and an aldehyde. Then you may recognize that the CH₂OH group can cyclize onto either carbonyl group with a mechanism as you have proposed.

[chmstud101]

I'm still having some trouble with this.  Are you saying that I started out correctly and just need to go farther or did I miss a step to begin with?  Thank you for your help.

[orgopete]

Okay, another hint. There are two carbonyl groups. R and R' are a H or an OH. Note that these reactions are reversible, so you could form the starting material from the right.