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CH 318L EXPERIMENT
Aim : To synthesize trans, trans-1, 4-diphenyl-1, 3-butadiene by using the WittigReaction method
Reagents :
Benzyltriphenyl phosphonium
chloride
dichloromethane
Ethanol trans-cinnamaldehyde
Sodiumsulphate(anhydrous)
Sodiumhydroxide
IUPACname
phenyl(phenylme
thyl)phosphoniu
m chloride
Dichloromethane
Ethanol trans -3-Phenyl-2- propenal
Sodiumsulphate
Sodiumhydroxide
Mol. Wt. .87g/mol 84.93g/mol
46.06844 g/mol
132.16g/mol 142.04g/mol
39.997g/mol
Density -- 1.33g/cm !
0.789g/cm !
1.05 g/cm ! at 25 C(lit.)
2.664g/cm !
2.13g/cm !
M.P 330 C -96.7 C -114 C " 9-" 4 C(lit.)
884 C 318 C
B.P -- 39.6 C 78.37 C
250-252 C(lit.)
1429 C 1,388 C
Apparatus : pipette, burette, conical flask, beaker, measuring cylinder, magneticstirrer, dropper, magnetic stirrer
Theory : The Wittig reaction is an organic chemistry synthesis technique that allowsthe creation of a new carbon-carbon bond. A nucleophilic addition reactionmechanism is adapted for the conversion of aldehydes and ketones into alkenes.
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Mechanism of Wittig reaction :
Step1: Ylide formation (Ylide is a neutral dipolar molecule with opposite charges onadjacent atoms and they function as carbon nucleophiles)
Step2:Betaine formation (Betaine is neutral dipolar molecule with opposite chargeson non-adjacent atoms)
Step3: Oxophosphetane formation (Oxophosphetane is a 4-membered ring withadjacent oxygen and phosphorous atoms)
Step4: Breakdown of oxophosphetane
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Hazards:
Serial No. Reagent Hazard Information
1 Benzyltriphenylphophoniumchloride
Toxic if swallowed
2 Trans- cinnamaldehyde Irritating to eyes, skin, respiratory system,may cause sensitization by skin contact
3 Sodium Hydroxide Corrosive, causes severe burns
4 Dichloromethane Irritating to eyes, skin, respiratory system,
5 Ethanol Highly flammable
6 Sodium Sulphate Irritant
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