Aaron Fernando Adol Condensations 4 29 2015 Abstract This lab we have an Aldol condensation reaction that will be experimented through reacting excess benzaldehyde with acetone and a strong base NaOH that will form a precipitate that will be washed with acetic acid and ethanol The product took less than 5 minutes to precipitate out of solution having approximately 68 72oC as the melting point The final yield was 0 34g calculated to be a 72 3 yield Introduction With basic condensation reactions carbonyl compounds may act as the electrophile or the nucleophile while having a net loss of water when combining the two molecules Aldol condensation reactions have an enolate ion reacting with a carbonyl compound to form a Bhydroxyaldehyde or B hydroxyketone Following by dehydration a conjugated enone is produced This type of condensation reactions is efficient in forming carbon carbon bonds and generally involves the nucleophilic addition of a ketone enolate to an aldehyde aldol The enolate ion adds as a nucleophile to the carbonyl electrophilic acceptor carbon Aldol condensation reactions between two aldehydes ketones are catalyzed in acidic or basic conditions and the product results from the addition of an aldehyde ketone molecule to the carbonyl carbon of the 2nd molecule Conjugation of the newly formed double bonds plus the carbonyl group stabilizes the unsaturated product and gives the thermodynamic favoring for dehydration to proceed The removal of water favors the reaction towards the products The order of events in the reaction initially involves the aldol formation subsequently the dehydration process First a strong base deprotonates the alpha carbon to the carbonyl group of the aldehyde ketone Then the enolate Aaron Fernando Adol Condensations 4 29 2015 ion will attack the carbonyl group of the molecule to drive the aldol towards an acid base reaction with the remaining acidic alpha hydrogen lastly followed by the loss of OH as a leaving group to give an enol and complete the reaction Chemical Reaction Aaron Fernando Adol Condensations 4 29 2015 Safety Full sleeved shirts pants and appropriate shoes worn Safety goggles gloves and apron worn through the whole lab period No food or drinks aloud during the lab period Used fume hood to ensure no potentially harmful chemicals were inhaled Careful handling all reagents knowing some are potentially dangerous When heating substances made sure the liquid being heated wasn t sealed tight and that air could escape Use caution to ensure not to burn on any heated objects All waste products were discarded in designated waste container Experimental The procedure for this experiment appears in Lab 9 Aldol Condensation 1 No changes made to the lab Results ADDUCT A1 USED NaOH 3 ml Ethanol 4 ml Acetone used 0 15 mL Density 1 045 Mass 0 898 g 2mmol Benzaldehyde used 0 812 mL Density 0791 mass 0 116 g 8 mmol Calculated Theoretical yield 0 468g Final product obtained 0 34g Percent Yield 72 3 Aaron Fernando Adol Condensations 4 29 2015 Time for precipitate roughly 3 5 minutes Observed Melting Point 68 72 oC Percent yield Actual Theoretical yield x 100 0 34 0 468g x 100 72 3 Theoretical Yield 002 mol 1 1 MW ketone 58 08g mol 2x MW benzalaldehyde 106 1g mol 36 1 468 grams Discussion Conclusion Running the aldol condensation reaction benzaldehyde and acetone were placed into solution for about 10 minutes roughly taking 3 minutes for percipitate to isolate out When isolated from solution by vacuum filtration the percipitate observingly was yellow The theoretic yield of product calculated was 0 468g while our product yielded 0 34g calculating to be a 72 3 yield The melting point obtained was roughly 68 72 oC which appears as a good sign since the melting range was low indicating the product is close to pure In the product formation acetone is intially deprotonated by the stong base NaOH at one of its methyl ends alpha to the ketone this produced a reactive carbanion that then proceeds to attack the benzaldehyde carbonyl The following protonation of the newly formed alkoxide occurs which creates the OH hydroxyl group that is a good leaving group followed by a elimination reaction taking the alpha carbons hydrogen to form an alkene with the hydroxyl group leaving Due to the fact we have excess benzealdehyde present the reaction happens quantively beginning with the deprotonation Aaron Fernando Adol Condensations 4 29 2015 of the carbon hydrogen next to the ketone however this time the opposite methyl group of the original acetone that hasn t yet reacted will be the area of interest The product yielded is a dibenzene that s connected through conjugated alkene and carbonyl bonds which came out to be a moleuclar formula and product weight of roughly 234 28g mol when added up Acetones unhindered properties compared to the other adducts allowed for the I believe is the reason for the quick reaction rate with benzealdehyde of approx 3 5 minutes to form percipitate which is why you told us to use benzaladehyde and acetone because you wanted us the hell out lab which was awesome Talking to my friends in other lab sections cyclohexanone and benzealdehyde reacting together took near 25 minutes for this being because cyclohexanone is a more hindered molecule This lab was pretty smoothly operated I do not have any additoinal feedback or suggestions to run it differetnly Even though our percent yield was low vaccum filtration for some groups might have been an issue when calculating the percent yields because of the water weight so potentially a differerent method of filtration might be more appropriate As for reasons to why our percent yield was low Potentially all the product was not tanseferred to the vaccum due to our vulnerabilty to human error there were absoultely some measureing or techinical mistakes along the way References 1 Ahsan Lab 9 Aldol Condensation Reaction Organic Chemistry Lab Notes Spring 2015