http://chemconnections.org/organic/chem227/deet-procedure-09.html
Background and Methodology:
Amides are usually prepared by treating a carboxylic acid derivative with ammonia or with a primary or secondary amine Acid anhydrides or esters are sometimes used as the acid derivative, but acyl chlorides are the most useful for preparing the widest variety of amides. Because of the high reactivity of acyl chlorides, the reactions are usually rapid and exothermic, so much so that, in many cases, the rate must be controlled by cooling or by using an appropriate solvent. When the reaction is carried out in an inert solvent such as diethyl ether or toluene, it is necessary to use at least a 100% excess of the nitrogen compound, because the reaction produces HCl which reacts with one equivalent of amine (or ammonia) to form the amine salt. This salt may also be difficult to separate from the product. One way to avoid these disadvantages is to add a base such as pyridine, triethylamine, or sodium hydroxide to react with the evolved HCl.
The synthetic method that uses aqueous sodium hydroxide (or potassium hydroxide) as the base is known as the Schotten-Baumann reaction. It has been used to prepare esters and other acyl derivatives as well as amides. Some acyl chlorides, particularly low-molecular-weight aliphatic ones, hydrolyze rapidly in water to form carboxylic acids and thus are unsuitable reactants for this procedure. However, aromatic and long chain aliphatic acyl chlorides are nearly insoluble in water and therefore hydrolyze much more slowly; the small amount of acyl chloride lost by hydrolysis can be compensated for by using an excess of this reactant. The presence of aqueous alkali in the reaction mixture also makes it possible to use an amine hydrochloride rather than the free amine, as the salt reacts with base to liberate the amine in situ . Since many amines are volatile, corrosive, and quite unpleasant to handle, the use of an easy to handle amine salt is an advantage.
The acyl chlorides used for preparing amides are generally themselves prepared from the corresponding carboxylic acids. Several reagents are commonly used for this reaction; each has certain advantages and disadvantages. Thionyl chloride (SOCl
2
) has the great advantage that all of the inorganic reaction products (HCl and SO
2
) are gases and can be easily removed from the acyl chloride, which is often used for further reactions without isolation.

In this experiment, you will first prepare m-toluoyl chloride by treating m-toluic acid with excess thionyl chloride. And, then without isolating the acid chloride, run a Schotten-Baumann reaction with diethylamine (from the amine hydrochloride salt) to prepare N,N-diethyl-m-toluamide
(DEET). Because corrosive acidic gases are released during the reactions, a sodium hydroxide gas trap will be used to keep them out of the lab environment. [NOTE: In the Schotten-Baumann reaction, efficient mixing is necessary to provide adequate contact between the water-insoluble acyl chloride and the amine. Use of the sodium lauryl sulfate, which acts like a detergent, helps disperse the acyl chloride into smaller particle sizes that increase the reaction rate.
]
After the product is isolated by extraction with ether, it can be purified by column chromatography. By comparing the infrared spectrum of the product with those of the starting materials, one can see evidence for the functional group conversions that have taken place. The proton NMR spectrum of the product consists of well-separated signals, which are easy to assign and useful to confirm the DEET structure.
PROCEDURE:
A. Preparation of m-Toluoyl Chloride
NOTE : All glassware must be thoroughly dried for this procedure. Carry out the reactions under a hood; equip the reflux condenser with a gas trap containing dilute NaOH.
Thionyl chloride and m-toluoyl chloride are both corrosive and lachrymators. They can cause severe damage to the eyes, skin, and the respiratory system. Thionyl chloride decomposes violently on contact with water to produce poisonous gases (HCl and SO
2
). Wear gloves, and work under a hood; avoid contact with thionyl chloride and the reaction mixture, keep them away from water, and do not breathe their vapors.
Under the hood, combine ~30 mmol of m-toluic acid with ~2.6 mL (~36 mmol) of thionyl chloride in a round bottom flask. Reflux the mixture gently for at least 20 minutes, until the evolution of gases stops. Cool the reaction mixture to ~10 o
C or below in an ice bath. Leave the m-toluoyl chloride under the hood in the stoppered reaction flask (supported in a small beaker) until you are ready to use it in the next step.
B. Preparation of N,N-Diethyl-m-toluamide
Diethylamine hydrochloride irritates the skin, eyes, and respiratory tract. Avoid contact and inhalation. In the reaction mixture, it forms diethylamine, which is corrosive and has toxic vapors. Diethyl ether is extremely flammable and may be harmful if inhaled. Do not breathe its vapors, and keep it away from flames and hot surfaces.
Reaction with Magnetic Stirring.
Assemble an apparatus for addition and reflux, using a 100mL round bottom flask equipped with a magnetic stir bar. Carry out the reaction out under a hood. Add ~35 mL of 3.0 M aqueous sodium hydroxide, and cool the flask in an ice bath. While stirring the NaOH solution, add ~25 mmol of diethylamine hydrochloride in small portions, followed by 0.1 g of sodium lauryl sulfate. Under the hood, transfer the cold m-toluoyl chloride from part A to the dry addition funnel; stopper the funnel immediately, and replace it on the reassembled reaction apparatus. Handle all materials under the hood.
Keeping an ice bath handy for moderating the reaction if necessary, slowly add the acid chloride to the reaction mixture while stirring vigorously. When the addition is complete, heat and stir the reaction

mixture over a boiling water bath for about 15 minutes. At this point, the acid chloride should be gone, and the reaction mixture should be basic to litmus.
Separation.
Cool the reaction mixture to room temperature or below, and extract it with three
20-mL portions of ethyl ether. Wash the combined ether extracts with 30 mL of saturated aqueous sodium chloride, dry the ether layer with magnesium sulfate, and evaporate the solvent.
It is unlikely that you will have time to proceed to the next step. It will take a minimum of 30 minutes (more like 45 minutes) so if you don’t have the time, don’t start this step!
Purification and Analysis: Purify the N,N-diethyl-m-toluamide by column chromatography record the IR spectrum and turn in.
The product can be purified by column chromatography. If it is purified by column chromatography, alumina should be used as the adsorbent (~4-5 cm of dry alumina in a 25-mmdiameter column), and the elution solvent should be petroleum ether. The first compound to elute will be N,N-diethyl- m-toluamide. Evaporation of the petroleum ether should give the purified amide as a pure colorless or light tan liquid (bp 160-163 o
C at 20 mm).
Report: Compare your spectrum with the IR spectra of the reactants . Point out important bands that have appeared, disappeared, or changed location in going from reactants to product, and tell how these bands provide evidence that the expected reaction has taken place. Have 1H nmr run on purified material and interpret the spectra as indicated by your TA.