Question

Determine the theoretical and percent yield for this lab

Wednerdouy 13 CH 4521-8: Crossed Aldol Condensation: Synthesls of trans-p-anisalacetophenone Ketones that contain an a-hydrogen (a hydrogen on the C right next door to the carbonyl group) can be tabilized via keto-enol tautomerization, or through the loss of the a-hydrogen to form an enolate anion. enolate anion Enolate ions actas nudbophiles and are considerable more reactive than tois. The enolate on i the subject of today's experiment. The formation of an enolate ion utilizes a base. The strength of the base required depends on how acidic the alpha-hydrogen is in the substrate. The a-hydrogens for aldehydes and ketones have an approximate pka of 18-20 (a pKa range similar to water and alcohols). The enolate ion is stabilized through resonance as the negative charge can be delocalized. Bases used to create enolate ions are hydroxide ons or alkoxide ions as the acidity of aldehydes and ketones is similar to that of water and alcohols Once the enolate ion is formed, it can act as a nucleophile and bond with the carbonyl carbon of the unreacted ketone or aldehyde present in solution. The mechanism for the base-catalysed addition is shown OH 1? ion base When the reaction is performed in wate or alcohol as the solvent, the source of the proton can be the solvent. Abstraction of the proton from water regenerates the hydroxide ion to act as a base for the next reaction (or removal of hydrogen from an alcohol generates the alkoxide lon). The base needed for this reaction is only added in catalytic amounts since it can regenerate through this process. The product of this reaction is called an aldol (it combines an aldehyde and an alcohol). The reaction is known as an "aldol addition reaction. The product may not be lsolated as an aldol since the base present in the reaction pot can perform an E2 elimination reaction and form the alkene product (a,B-unsaturated carbonyl 67

Answer 1

p-Anisaldehyde Mol. Wt.: 136.15 Density: 1.119 g/mL 1 mL. 1.119 g, 8.2188 mmol Limiting reactant Acetophenone Mol. Wt.: 120.15 Density: 1.03 g/cm3 1 mL. 1.03 g, 8.5726 mmol Etahnolic NaOH Aldol reaction trans-p-anisalacetophenone Mol. Wt.: 238.28 8.2188 mol Theoritical yield: 19583 g Actual yield-0.205 g (as written by you) Percentage yield- (Actual yield / Theoritical yield) x 100 - (0.205/1.9583 )x 100 10.46 %