Reactions

Groupwork #2

- Salicyclic acid is C₇H₆O₃ : 1-hydroxy-2-carboxy- benzene, I.e., the hydroxy group -OH is on one benzene carbon and on an adjacent carbon of the benzene is a carboxylic acid group –COOH.

- Methanol is H₃COH

b) Identify which atoms are most electronegative, then, shift electron density in bonds toward all electronegative atoms.   Now, which atoms have less electron density?  Does this suggest which atoms are reactive?   What kind of reactivity will they exhibit?

O atoms in the salicylic acid are the most electronegative; this will result in making adjacent C atoms moe electron poor. The C atom bond to two O's,

like -C(=O)-OH will be the most electropositive atom and it will react to get more electron denisty.

c) What are the electrophilic and nucleophilic atoms in the reagent molecules? Identify which two centers predominate in the reaction.

In methanol, the single O atom is a nucleophilic atom. In salicylic acid, the C atom of the carboxylate,

-C(=O)-OH will be the most electronegative atom.

d) Use your models to show the reaction of the electrophile and nucleophile by using a long bond to join the reacting atoms.

The product of the reaction is an ester and its structure is below. What does its odor remind you of?

this is known as oil of wintergreen

Given the above structure, what atoms must be lost from the reagents? (hint: look at your intermediate structure you made with your model molecules in part (e) and compare to product above.

A molecule of water, H2O , must be lost form the intermediate made from methanol+salicyclic acid.

f) No reaction happens without addition of sulfuric reaction. What’s the effect of adding the STRONG acid H2SO4?

The acid catalyzes the reaction and makes it go faster.

g) Draw a reaction showing salicyclic acid acting as a Lewis base towards H2SO4. (yes, this is odd! But just proceed using only your knowledge of the definition of a Lewis Base.

The strong acid H2SO4 can protonate the C=O group and the -O-H groups of salicyclic acid, making the carboxylate C atom even MORE electrophilic.

h) Can you explain why salicylic acid could become protonated by sulfuric acid?

Sulfuric acid is very strong, and can donate a H+ to the lone pair electrons of the O atoms.

How will protonating salicyclic acid affect the reaction with methanol, how might it help or hinder?

The strong acid protonates the C=O group of salicyclic acid, making the C atom even MORE electrophilic.

i) What structural piece(s) are the same for these two aromatic molecules, oil of wintergreen and jasmine?

both have an ester group, -C(=O)-O-