DEET Lab #4

What is DEET?

N,N-Diethyl-m-toluamide

What is DEET used for?

Insect repellent

How does DEET work?

Blocks insect detection of lactic acid and body signals

What diseases are prevented by using DEET?

Malaria and West Nile Virus

What type of reaction is used to make DEET?

Amide formation

What starting material is used?

m-toluic acid

What reagent converts carboxylic acid to acyl chloride?

Thionyl chloride (SOCl2)

What intermediate is formed after SOCl2 reacts?

Acyl chloride (m-toluoyl chloride)

What is the nucleophile in the second step?

Diethylamine

What type of mechanism forms DEET?

Nucleophilic acyl substitution

Why can't amines react directly with carboxylic acids?

Acid-base reaction prevents amide formation

How do we fix this problem?

Convert acid to acyl chloride

What makes acyl chlorides more reactive?

Good leaving group (Cl⁻)

What procedure is used in this lab?

Schotten-Baumann reaction

What base is used instead of excess amine?

NaOH

Why use NaOH instead of excess amine?

Cheaper and greener

What does NaOH do in the reaction?

Neutralizes HCl and forms free amine

Why is the reaction kept basic?

Ensures amine stays nucleophilic

What happens if solution is not basic?

Amine becomes protonated and unreactive

What solvent system is used?

Aqueous conditions

What is used to emulsify the reaction?

Detergent (sodium lauryl sulfate)

What type of reaction setup is used on Day 1?

Reflux

What indicates reflux is happening?

Condensation in condenser

What solvent is used for extraction?

Diethyl ether

Where is the organic layer in ether extraction?

Top layer

Why wash with HCl?

Remove leftover amine

Why wash with brine?

Remove water

What drying agent is used?

Sodium sulfate

What purification method is used?

Column chromatography

What is the stationary phase in column chromatography?

Alumina (polar)

What is the mobile phase?

Hexanes (nonpolar)

How does chromatography separate compounds?

Based on polarity

What moves faster in column chromatography?

Less polar compounds

What analysis methods are used?

IR, 1H NMR, GC/MS

What IR peak indicates amide formation?

C=O stretch (~1650–1700 cm⁻¹)

What peak disappears from starting material?

O–H (carboxylic acid)

What does GC/MS tell you?

Purity and molecular fragments

What does NMR tell you?

Hydrogen environments

Why do amides show restricted rotation?

Resonance gives partial double bond character :contentReference[oaicite:0]{index=0}

What is the activation energy for amide rotation?

~17–20 kcal/mol

How does temperature affect NMR signals?

Higher temp = faster rotation = peaks merge

What happens at low temperature in NMR?

More distinct peaks (less rotation)

What happens at high temperature in NMR?

Peaks become equivalent

Why should the reaction be strongly basic after adding NaOH?

To stabilize the product and ensure reaction proceeds

What is correct for TLC procedure?

Run crude, pure, and mixed samples

What happens if stir bar does not spin properly?

Product yield decreases significantly

How many equivalent hydrogen groups in DEET at high temp?

Fewer due to rapid rotation

What precaution is NOT taken with thionyl chloride?

Adding water directly

What safety precautions are required?

Gloves, goggles, fume hood