1 Answer | Add Yours
We are talking about two different chemical reactions here, both of which are prevalent in biological systems. The first reaction is the dehydration reaction. This involves the loss of water from a molecule. It occurs most commonly when the hydroxyl group (OH) of an alcohol is eliminated to produce a double bond. A hydrogen cation (called a proton) is removed from a carbon atom adjacent to the alcohol. The resulting negatively charged pair of electrons goes between the carbon atoms to make a double bond, and the OH group is eliminated. The H+ and OH- groups join to become water (H2O). A general example of propanol dehydrating to propene is shown below.
CH3-CH2-CH2-OH ---> CH3-CH=CH2 + H2O
The second reaction is a hydrolysis reaction. This is where an ester group is reacted with a water molecule to produce a carboxylic acid and an alcohol. An example is shown below.
Et-C(O)-OCH3 + H2O --> Et-C(O)-OH + CH3OH
The water molecule essentially attacks the ester carbonyl carbon and the alcohol is removed. So the water molecule becomes part of the carboxylic acid. This is all a little hard to draw out precisely here, so see the images in the links below.
We’ve answered 330,820 questions. We can answer yours, too.Ask a question