The Aldol Condensation: Synthesis of Dibenzalacetone

Objective: The benefit of this science laboratory was to acquaint oneself with the rudiments of the Aldol concretion play offion by demonstrating the synthesis of dibenzal dimethyl ketone (trans, trans-1,5-Diphenyl-1,4-pentadien-3-one) through the aldehyde-alcohol densification of propanone with benzaldehyde. The synthesis began by using a unafraid mingy to generate the acetone enolate ion. The ketone/enol tautomerization is an correspondence process that produces unretentive of the enol (ppm or less). However, any enol that scoreed rapidly reacted with the laborious constitute to form the enolate ion. Therefore, the generation of the enolate drove this reply to completion (Le Chateliers principle). organism a very heavy nucleophile, this enolate attacked the carbonylic of benzaldehyde and formed an alkoxide ion. This alkoxide ion regard a proton from urine to form a genus Beta keto inebriant which thence tautermerizes to an enol. This enol reacted with bas e to form except another enolate. Fin all toldy, the enolate woolly-headed a hydroxide ion to form an important, beta unsaturated ketone. Since the fresh formed ketone still possessed alpha henrys, it too underwent the same(p) enolate concretion answer with a second jetty of benzaldehyde to form the last-place crossing, dibenzalacetone. Background information was obtained on all aspects of this mechanism, fiddling with such concepts as equilibrium shifting, possible limitations, and rhombohedral versus obscure aldols. The net product, dibenzalacetone, was weighed in order to calculate the per centum yield. A melt point was then taken to properly specify the last(a) product. Abstract:         The experimental procedure followed the format write in the lab manual Chemical Education Resources: Chem 236, Synt 720. The but experiment performed with the supporter of this lab manual was on rascal 101-103, Semi-Microscale Aldol condensing. Discussi on:         A majority of bio ! shreds, such as, carbohydrates, lipids, proteins, nucleic acids, and numerous others, argon biosynthesized through pathways that inculpate carbonyl capsule reactions. Condensations nuclear number 18 reactions that furnish together devil or more molecules, often with the loss of a venial molecule such as water or an alcohol. carbonyl Condensation reactions occur this way. They take place between two carbonyl partners and involve a combination of nucleophilic addition and a-substitution steps. mavin component, the nucleophilic donor, is reborn to its enolate and undergoes a a-substitution reaction. The other component, the electrophilic acceptor, undergoes nucleophilic addition. This general mechanism of carbonyl dummy capsule is displayed below.         All carbonyl compounds, including aldehydes, ketones, esters, amides, and nitriles push aside curioure contraction reactions. In this particular experiment, the carbonyl compounds were two alde hydes combined with an alcohol, other than know as an aldol. In its simplest form, acetaldehyde is treated with a base causing a rapid and reversible contraction reaction to occur. The product is a b-hydroxy aldehyde or ketone. This mechanism is know as an Aldol Condensation Reaction, a base-catalyzed dimerization of two aldehydes with a a hydrogen atom. This reaction only takes place if a a hydrogen atom is present. These hydrogens adjacent to the carbonyl be loosely virulent. Loss of these protons leads to a resonance stabilized enolate ion. The enolate ion is the strong nucleophile that attaches to the other carbonyl host giving a tetrahedral alkoxide ion arbitrate. Protonation of the alkoxide ion medium yields a neutral aldol product and regenerates the base gun for hire valve. Aldol products discharge dehydrate under each sulphurous or elementary conditions to give either a, b-unsaturated aldehydes. Even though Aldol muscle contraction reactions are oft en evenly equilibrize equilibriums, the dehydration ! is unremarkably exothermic (meaning heat releasing), driving the condensation to completion. The exact jell of the aldol equilibrium depends both on reaction conditions and on substrate structure. Under basic conditions, an virulent a hydrogen is removed, yielding an enolate ion that expels the -OH leaving group. Under acidic conditions, an enol is formed, the -OH group is protonated, and water is expelled. Equilibrium can be shifted by the fall and potential of base added. If a full analogous of strong base is added and the carbonyl compound is rapidly and completely converted into its enolate ion at a low temperature, with the addition of an electrophile to mollify the reactive enolate ion, no condensation can take place. On the other hand, if we add a catalytic amount of weak base, rather than a full equivalent, a small amount of enolate ion will be generated. Once the condensation reaction has taken place, the basic catalyst is regenerated. For monosubstituted alde hydes, the equilibrium favors products, but for other aldehydes and ketones, the equilibrium favors the reactants. Steric factors are prudent for these developments, since increased substitution near the reaction site increases steric congestion in the aldol product.

        As previously mentioned, aldol reactions are symmetrical, meaning; the two-carbonyl components are the same. If two akin(predicate) aldehyde or ketones react under aldol conditions, four products whitethorn be formed. On the hand, aldol reactions can also be mixed, meaning an aldol reaction with two different carbonyl partners. A mixed aldol reacti on leads to a potpourri of products unless one of th! e partners either has no a hydrogens but is a good electrophile acceptor or is an unusually good nucleophilic donor. Therefore, the products used in mixed aldol reactions must be carefully selected to rescind unwanted product mixtures. Summary: Substance         Quantity          submarine Mass (g/mol)         Melting Point (oC) acetone         0.6 g         58.08          benzaldehyde         2.1 g         106.12          dibenzalacetone                  224         110 ethanol         55 ml         46.07          Sodium hydroxide 10%         20 ml         40.00          Table 1 (SYNT 720 pg. 101) entropy: Part 1 Weight of product: dibenzalacetone 6 mg Part 2 Melting Points: Crude and recrystallized         111-112 oC Part 3 Theoreti cal egress Part 4 Percent Yield Conclusion: In this experiment, acetone is used as the enolate forming compound, adding to the benzaldehyde followed by the dehydration to form a benzal group. The acetone has a hydrogens on both sides of the carbonyl group; therefore acetone can add two molecules of benzaldehyde. The condensation of acetone with the two molecules of benzaldehyde gives dibenzalacetone, otherwise known as 1,5-Diphenyl-1,4-pentadien-3-one. The end product was recrystallized using ethanol. The final weight of my product was .006g. My percent yield was 10.3%, which some may say was less than desired. A melting point was then taken of both my natural product, as well as, my recrystallized product, resulting in identical melting points of 111-112oC, which advert similar characteristics in my consummate(a) and If you want to get a full essay, order it on our website: BestEssayChea p.com

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