So how did Carothers prove that macromolecules could exist? He did so by carrying out some very basic chemistry. He knew that an alcohol and a carboxylic acid will react, catalyzed by hydrochloric acid (HCl) to make an ester. For example, acetic acid will react with ethanol to produce ethyl acetate, a very smelly compound:
So Carothers figured that if he used acids and alcohols that could react at both ends, he'd get long chainlike molecules, like this:
Since no other reactions happen when the ester, the alcohol, and HCl are brought together, if any reaction at all occurred it would have to form macromolecules. When Carothers and his team of scientists tried this, there was a reaction all right, and the products were macromolecules, with molecular weights as high as 20,000. Macromolecules were no longer just a theory. They were now an accepted fact.