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Lab Exam Preparation

Course Code
Wanda/ Lana
Study Guide

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Dehydration of Cyclohexanol
oAcid catalyzed dehydration of cyclohexanol to form cyclohexene using a distillation
oPurify through microextraction and microfiltration
oDehydration = -H2O and form double bond (E1 mechanism)
oAcid catalyst otherwise (-OH) not good LG
Separate according to bp
Cyclohexene (83 C) and Cyclohexanol (161 C)
Thus, cyclohexene extracted but as an azeotrope
oMicroscale- Extraction
Need to separate azeotrope (Cyclohexanol + H2O + Cyclohexene)
Based on different solubilities
Use saturated salt solution NaClwhy?
Cyclohexanol more soluble in polar salt solution
Cyclohexene non-polar thus not soluble in salt solution
Remaining water removed by adding anhydrous Na2SO3 and doing
microfiltration to removing (sodium sulphate + H2O)
o2nd distillation
React any remaining cyclohexanol
Xylene chaser added – why?
Chaser = solvent added to increase volume but doesnt react with product

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Xylene (bp = 140 C)—thus appropriate
Purified using microextraction and microfiltration
oFirst distillation
Simple distillation apparatus
Cyclohexanol + Phosphoric acid and distil
Watch for a bead of condensate on thermometer
Not too rapid – decreases yield
oMicroscale-Extraction + Microfiltration
Boiling tube (aka test tube)
Transfer distillate into boiling tube and add 2X 5ml of saturated NaCl
Use pipette to mix
Drain aqueous layer bottom layer
Thus, leave the non-polar cyclohexene
Add anyhydrous Sodium Sulphate
Microfiltration apparatus
Glass wool in Pasteur pipette
Pour solution through glass wool using another pipette into a RB Flask
Rinse with xylene
oSecond distillation
Add xylene to previous residue of distillation and distil and purify using
microextraction and microfiltration
Mix products
Synthesis of DEET

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oSynthesize N,N-diethyl-m-toluamide (DEET) using reflux and extraction techniques
oTwo steps
M-toluic acid + SOCl2 m-toluoyl chloride + SO2 + HCl
Use SOCl2 in ether chlorination
SOCl2 why?
oProduce high yields and few purification problem
oSO2 and HCl bubble out of reaction thus shift to the products
M-toluoyl + 2 Et2NH DEET + HCl
Why 2 moles of Et2NH?
o1 mole for reaction
o1 mole for HCl neutralization
oChange remaining m-toluoyl chloride back into m-toluic acid
Basic (10% NaOH)
oM-toluic acid to its water soluble carboxylate salt
oThus, remove unreactive carboxylic acid
Acidic (HCl)
oProtonates diethyl amine (basic N) thus, removing it.
oWhy does it not affect DEET?
It contains non-basic nitrogen
Evaporate excess ether leaving oily product
Soap and Detergents
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