In: Chemistry
Please no cursive
1) Draw the structure of caffeine and determine the most basic nitrogen and specifically explain your rationale with the use of Lewis structures. You may need to research this.
2) The purpose of synthesizing a caffeine derivative involves melting points. Draw the structure of the specific derivative from THIS experiment, and explain how it differs from caffeine.
1.
N1 is sp2 hybridised. The “lone pair” is in the
unhybridised p orbital and is part of the aromatic system so is
unavailable to act as a proton acceptor.
N2 is also sp2 hybridised, but here the lone pair is in
the sp2 hybrid orbital pointing away from the ring system. It is
able to act as a proton acceptor, so this N is basic.
The “lone pairs” on the two N’s in the 6-membered ring are (atleast
partially) involved in the resonance stabilisation of the amides
and the aromatic system as shown in the below-
These electrons are
delocalised and hence not available to act as proton acceptors, so
not basic.
2) Caffeine is a base which can react with acids to form salts. A well characterized salt of caffeine is caffeine salicylate formed by using salicylic acid. This derivative of caffeine has an accurate melting point.The structure is given below-