# What is the reaction between piperine and concentrated sulfuric acid?

Piperine was chemically characterized by reaction with acids. This was done by dropping concentrated $$\ce{HNO3},$$ $$\ce{HCl},$$ and $$\ce{H2SO4}$$ to a sample of piperine. Both $$\ce{HNO3}$$ and $$\ce{HCl}$$ produced yellow solutions while sulfuric acid produced a blood-red solution.

What happens to piperine as it reacted with $$\ce{H2SO4}$$ and why it turned blood-red? Also, what is the difference of that reaction with the reaction of piperine with $$\ce{HNO3}$$ and $$\ce{HCl}?$$

Edit: Late addition for viewer's convenience:

The piperine structure is shown below:

• Would help if you gave the structure of Piperine – Waylander Sep 24 '19 at 10:49
• Interesting question... The reactions with the acids have likely changed the conjugated system, thus resulting in different wavelengths of light being absorbed by the resultant compounds. Nitration may occur with conc. nitric acid but as to why both nitric acid and hydrochloric acid both give a yellow solution, it is indeed puzzling. – Tan Yong Boon Sep 24 '19 at 14:44
• The methylenedioxyphenyl system is very electron rich so protonation seems a possibility – Waylander Sep 24 '19 at 16:38
• @Waylander: I have added the structure for your convenience. – Mathew Mahindaratne Sep 24 '19 at 16:39