Reducing Agents

Overview

Source: Vy M. Dong and Daniel Kim, Department of Chemistry, University of California, Irvine, CA

Controlling the reactivity and selectivity during the synthesis of a molecule is very important criteria for chemists. This has led to the development of many reagents that allow chemists to pick and choose reagents suitable for a given task. Quite often, a balance between reactivity and selectivity needs to be achieved. This experiment will use IR spectroscopy to monitor the reaction and to understand the reactivity of carbonyl compounds as well as the reactivity of hydride-reducing reagents.

Procedure

1. Measuring Properties of Ethyl Acetoacetate

Take an IR of the starting material (ethyl acetoacetate).
Take a TLC using 40% ethyl acetate in 60% hexanes.

2. Reduction of Ethyl Acetoacetate with Sodium Borohydride

Add 1 mmol of ethyl acetoacetate to a round-bottom flask.
Add 5 mL of ethanol and swirl to mix completely.
Lower the beaker into an ice-water bath.
Weigh 1 mmol of sodium borohydride and slowly add to the stirred

Results

Figure 1. Representative IR results for ethyl 3-hydroxybutyrate.

Application and Summary

The trends of carbonyl reactivity and hydride donor ability have been reviewed and demonstrated. The visual reactiveness of the two commonly used reagents is apparent and can be appreciated.

The understanding of the reactivity of reagents and functional groups is of high importance when developing new methods for reductions or any other kind of reaction. Controlling the selectivity and reactivity of any reaction is an important factor to consider when deciding on the reagents used for a chemic