CHM 2123 Study Guide - Final Guide: Methanol, Sodium Chloride

THEORY Esters can be made by a variety of reactions. The n-butyl acetate synthesis performed in this lab illustrates the most fundamental method of preparing esters, the Fischer esterification, corresponding to the general equation: H2SO4 + H2O When a carboxylic acid and an alcohol are reacted together in this manner, a strong mineral acid (for example, H,SO) is usually added to catalyze the reaction. R' and R can be any organic group (alkyl, alkenyl, alkynyl, aryl) and they do not have to be the same. n-Butyl acetate is added to a variety of commercial products to create fruit flavours, especially apple, pear, and banana. This ester can also be used as a solvent for laquers, enamels, plastics, leather finishing, rubber and camphor. The "Competition Experiment" section of this lab provides an example of another method of making esters - the reaction of alcohols with carboxylic acid chlorides. UNDERSTANDING THE EXPERIMENT During the two week period since your last lab, the esterification reaction has been proceeding and hopefully will have gone to completion. To separate the desired product from unreacted starting materials and unwanted side products, a distillation is performed. The distilled product will be contaminated with trace amounts of acid and, thus, a neutralization step and drying with MgSO, to remove traces of water are required to obtain reasonably pure product. In the competition experiment, two different alcohols will compete for pivaloyl chloride in the esterification reaction. Which alcohol will win? TLC analysis of the reaction will reveal the answer.

Coot Frix, №.tutall ered.nt 16 EXPERIMENT SYNTHETIC SNAPDRAGON SCENT: FISHER ESTERIFICATION OF BENZOIC ACID 0 In this experiment a Fisher esterification reaction will be performed to prepare methyl benzoate, the princi- the snapdragon lower's scent. Read the sections of your lecture text dealing with the Fisheres terification of carboxylic acids prior to coming to lab Esters are derivatives of carboxylic acids and are utilized by nature for a variety of tasks. The ester that will be prepared in this experiment is a major scent component of the snapdragon flower The lower synthesizes methyi benzoate as an attractant for pollinating insects from benzoic acid and S-adenosylmethionine (SAM) as shown in Scheme 16.1. You should note that this reaction is a simple Sy2 type reaction where the SAM functions in a similar fashion to methyl iodide. You can learn more about meth tant by reading the article found in the journal The Plant Cel! ylbenzoate as an insect attrac- iNegre. E kish, C. M.; B at right,Ji Underwood B., Shibuya K·Wagner, Ci dirk. D G. Dudareva, N. The Plant G 2003, 15, 2992

THEORY Esters can be made by a variety of reactions. The acetate synthesis performed in this lab m illustrates the most fundamental method of preparing esters, the Fischer esterification corresponding to the general equation: H SO R2-OH R1 OH R1 OR When a carboxylic acid and an alcohol are reacted together in this manner, a strong mineral acid (for example, HSO is usually added to catalyze the reaction. R and R can be any organic group (alkyl alkenyl, alkynyl, ryl) and they do not have to be the same. n-Butyl acetate is added to a variety of commercial products to create fruit flavours, especially apple, pear, and banana. This ester can also be used as a solvent for laque plastics, leather finishing, rubber and camphor The "Competition Experiment" section of this lab provides an example of another method of making esters the reaction of alcohols with carboxylic acid chlorides. UNDERSTANDING THE ExPERIMENT the two week period since your last lab, the este has been hopefully will have gone to completion. To separate the desired product from unreacted starting materials and unwanted side products, a distillation is performed. The distill product contaminated with trace amounts of acid and, thus, a neutralization step and drying M to remove traces of water are required to with obtain reasonably pure product. In the competition experiment, two different alcohols will compete for pivaloyl chloride in the esterification reaction. Which alcohol will win? analysis of the reaction will reveal the answer.