8 - Aldol Condensation of Isatin and Acetophenone

8 - Aldol Condensation of Isatin and Acetophenone -...

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Unformatted text preview: Experiment #8: Aldol Condensa5on of Isa5n and Acetophenone Objectives: •  To synthesize an α,β unsaturated ketone from 2 ketones using diethyl amine as a catalsyt. •  The α,β unsaturated ketone will then be reduced using sodium dithionite •  To purify the product through a recrystalliza5on. •  To iden/fy and analyze purity through TLC and mel5ng point analysis. •  Calculate the yield Before coming to lab… •  Review these techniques: –  Recrystallization –  Melting Point Analysis ALDOL CONDENSATIONS •  Aldol condensations are nucleophilic additions of an enolate ion, which are strong nucleophiles, to another C=O group under basic conditions. •  Protonation gives the aldol product. •  Once formed, the aldol product undergoes dehydration in base. •  Abstraction of an a proton gives an enolate that can expel an –OH ion to give a conjugated product. •  Dehydration is usually exothermic because it leads to a very stable conjugated product. CHEMICAL EQUATION Aldol Mechanism In this lab…. •  Use reac5on mixture prepared during lab 7 •  Perform aldol followed by subsequent reduc5on using sodium dithionite •  Use color of compounds to iden5fy structures Conjuga5on and color •  Ground state and excited state of electrons are closer in energy than nonconjugated •  Lower energy light needed to excite electrons •  Highly conjugated system will absorb lower energy po5ons of light and reflect what is not absorbed. Conjuga5on and color Violet: 400  ­ 420 nm Indigo: 420  ­ 440 nm Blue: 440  ­ 490 nm Green: 490  ­ 570 nm Yellow: 570  ­ 585 nm Orange: 585  ­ 620 nm Red: 620  ­ 780 nm •  Less conjugated will absorb higher energy por5on of spectrum and lower energy parts are reflected to eye. Color and conjuga5on ...
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