Question

Theobromine (C7H8N4O2; M=180.2 g/mol) is an alkaloid found in chocolate.

1)Despite having several nitrogen atoms in its sturcture, it is an extremely weak base in water. Provide a reasonable explanation for this behavior?

2)Propose and draw a structural modification to the molecule of theobromine that would transform the substance into a stronger base. Justify your reasoning.

Answer 1

1)Inspite of having so many N atoms in theobromine it is considered a very weak base..The reason is quite observatory when we look at its structure ...There are 2 carbonyl groups attached to the adjacent of N atoms and we know that carbonyl groups shows Minus inductive effect and minus mesomeric effect due to the absemce of any lone pair in carbon atom of carbonyl in any compound...Hence due to -I and -M effects carbonyl groups makes a partial postive charge on N atoms which makes it to loose the H atom attached to it..so that it may gain electrons..though it has lone pairs but due to these minus eefects of carbonyl groups makes it less electronegative...hence Theobromine loose its tendency to gain protons and become a base which is very uncomman.

2)I will be definitely relplacing carbonyl groups with such groups which shows +I and +M effects to the whole compound ...this will also increase the electron density near N atoms attached adjacent to them..making it electron rich center and in this way it can easily be attacked by a proton resulting in theobromine to be called as a strong base then...such as OH- , Cl- , CH3-....