Question on the rxn of Alcohol and Carboxylic acids.

[wasteofo2]

I've got some questions about the reaction of Alcohol with carboxylic acids, and the behavior of the esters formed.

1) Is there a way to determine how molar an alcoholic solution is by it's % alcohol by volume?

2) If you have determined how many moles of alcohol there are in a liquid and how many moles of Acid there are, is there anything else to factor into their reaction besides that? If you have 2 moles of Aceitic acid in solution, and add 4 moles of alcohol in the solution, will you invariably end up with 2 moles of esters, or are there other things that could play a role in this reaction, such as other ions or molecules dissolved in solution along with the alcohol and acid?

3) How rapid is the formation of esters in a solution with both alcohol and carboxylic acids?

4) Will esters immediately evaporate out of solution once they are formed?

Thanks a lot,
Jacob

 

[GCT]

1) Is there a way to determine how molar an alcoholic solution is by it's % alcohol by volume?

yes, I would imagine one can use ethanol's density to do so.

2) If you have determined how many moles of alcohol there are in a liquid and how many moles of Acid there are, is there anything else to factor into their reaction besides that? If you have 2 moles of Aceitic acid in solution, and add 4 moles of alcohol in the solution, will you invariably end up with 2 moles of esters, or are there other things that could play a role in this reaction, such as other ions or molecules dissolved in solution along with the alcohol and acid?

well in any chemical reaction you'll want do achieve things in a controlled fashion, and there are standard methods of achieving transesterification. In this case acetic acid will be the limiting agent, but they will react in a one to one ratio. The percent yield will vary, you probably will not obtain the theoretical yield.

3) How rapid is the formation of esters in a solution with both alcohol and carboxylic acids?

I've never actually performed the experiment before, but I imagine it can be done in about 15 minutes.

4) Will esters immediately evaporate out of solution once they are formed?

well, once again there are standard experiments for this particular reaction which I'll need to search for, don't have the time right now. I don't believe that they will evaporate from the mixture, you'll need a particular experimental method to accomplish this. You'll might be able to obtain through vacuum filtration as a solid, at cooled temperatures.

 

[movies]

In my experience with Fisher esterification reactions, they usually run overnight at reflux. I've never formed an ester that was volatile enough to evaporate from the solution so I can't say whether that is problematic or if there is a spiffy solution. Often I think the reaction is actually done well before the night is through, but that insures complete conversion to product. You can get nearly quantitative yield from this reaction (last time I did one I got 99.1%)