Evaluation of L – Proline as a Catalyst for an Asymmetric Aldol Reaction

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Evaluation of L – Proline as a Catalyst for an Asymmetric Aldol Reaction

This reaction is divided into two parts. In the first part acetone, L – proline and 4 – nitrobenzaldehyde are reacted to give (R)-4-hydroxy-4-(4-nitrophenyl)butan-2-one as the major product along with (S)-4-hydroxy-4-(4-nitrophenyl)butan-2-one. The identity of the product is confirmed by IR spectra of the product which gives peaks at 1073.94 cm-1, 1330 cm-1, 1515.05, 1600.13 cm-1, 1708.25 cm-1, 2930.82 cm-1and broad peak at 3418.10 cm-1. The mass of the product is 0.013 grams which gives a percentage yield of 29.81%. The melting point of the product is not taken due to minimal product.
In the second part of the reaction excess reagents are used and the synthesized product is in very small quantities. The product synthesized is diastereomers of 1-(4-nitrophenyl)-3-oxobutyl 3,3,3-trifluoro-2-methoxy-2-phenylpropanoate. The identity of this compound is confirmed by the following peaks seen in 1H NMR: 8.19 and 7.62 ppm, 5.47 ppm, 2.90, 2.13 ppm, 3.30 ppm, 7.36 – 7.38 ppm. The melting point, IR spectrum, theoretical yield or percentage yield is not found since all of it used in 1H NMR analysis. The product 1H NMR shows a mix of both the diastereomers, but it is difficult to ascertain which one is in excess.
The aldol reaction that was experienced in this lab is the nucleophillic addition of an enolate to a carbonyl group to form a B-hydroxycarbonyl. This reaction is a very powerful method to construct of carbon-carbon bonds. Nature has developed the aldolase enzymes that catalyze biological aldol reactions. Aldolase is the enzyme that produces only one enantiomeric product that is hard to achieve. A simple amino acid L-proline can be used as the aldolase catalyst in asymmetric aldol reaction of acetone with a variety of aldehydes. This method produced 68% and 76% of…...

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...ARTICLES PUBLISHED ONLINE: 15 DECEMBER 2014 | DOI: 10.1038/NCHEM.2131 Copper-catalysed selective hydroamination reactions of alkynes Shi-Liang Shi and Stephen L. Buchwald* The development of selective reactions that utilize easily available and abundant precursors for the efficient synthesis of amines is a long-standing goal of chemical research. Despite the centrality of amines in a number of important research areas, including medicinal chemistry, total synthesis and materials science, a general, selective and step-efficient synthesis of amines is still needed. Here, we describe a set of mild catalytic conditions utilizing a single copper-based catalyst that enables the direct preparation of three distinct and important amine classes (enamines, α-chiral branched alkylamines and linear alkylamines) from readily available alkyne starting materials with high levels of chemo-, regio- and stereoselectivity. This methodology was applied to the asymmetric synthesis of rivastigmine and the formal synthesis of several other pharmaceutical agents, including duloxetine, atomoxetine, fluoxetine and tolterodine. C omplex organic molecules play a crucial role in the study and treatment of disease. The extent to which they can be utilized in these endeavours depends on the efficient and selective chemical methods for their construction1. Amines are widely represented in biologically active natural products and medicines2 (a small selection of which are shown in Fig. 1a). Consequently, the......

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...Laboratory Exercise Two Reaction Enthalpies for Acid – Base Neutralization Reactions Goals 1. To measure the amount of heat released in acid-base neutralization reactions. 2. To determine the molar enthalpy change for each acid-base neutralization reaction. 3. To validate Hess’s Law using the experimental results. Background Information Acids and bases react together to produce a salt and water as shown in the following reaction. HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l) This type of reaction is called a neutralization reaction. When a neutralization reaction occurs, heat (q) is released to the surroundings, and the temperature of the surroundings rises. In aqueous acid-base neutralization reactions the surroundings are the solution itself, which is mainly composed of water. The amount of heat released by the reaction can be determined by measuring the temperature change of the solution during the reaction. At constant pressure, the heat released by a reaction is the reaction enthalpy (∆Hr). The units for reaction enthalpies are kJ mol-1; in reactions that don’t have a 1-to-1 ratio of all reactants and products, we need to specify per mol of which species. In this experiment, the heat released by each reaction will be used to determine the reaction enthalpy for each chemical reaction per mole of acid reacted. (Note that this may or may not be the same thing as “per mole of acid added;” you will need to think about limiting reagents.) During the experiments the temperature......

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...212 g (pure product) | Percentage Yield Calculations: Supporting Data and Documentation: Name | Data | Benzaldehyde | 2.683 g | Acetone | 0.776 g | NaOH | 2.514 g | Water | 25 mL | Ethanol | 20 mL | Empty funnel | 15.597 g | Funnel with crude product | 18.959 g | Empty funnel | 15.786 g | Funnel w/ pure product | 17.998 g | Melting pt range (crude product) | 101˚C | Melting pt range ( pure product) | 105˚C | Results and Discussion: In this experiment the ethanolic solution composed of Acetone and Benzaldehyde were added to the aqueous sodium hydroxide. The two moles of belzaldehyde acted in response with both acidic α-protons of the acetone. Throughout the combination dehydration of the aldol product occurred. Dibenzalacetone, the final product, was precipitated right after mixing all the solutions with a yellow color and a pleasant smell. The product was then filtered from the combination, washed away, constrained dried and recrystallized from the hot ethanol. Melting point range were determined after crystallization with 101˚C and recrystallization with a 105˚C, which is very close to the melting point in the text book (113˚C). Percent yield of the recrystallization was calculated with a 72.62 %. Some of the final product was lost while doing the recrystallization. Infrared Spectroscopy was also determine. The IR Spectrum was very similar to the one in the book. The first peak......

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...Evaluation Wal-Mart is an organization that believes in having an effective evaluation process for its managers. An effective process will provide the necessary needs for learning and improvements on how to be a manager. Wal-Mart training process provides opportunities for managers throughout their careers. The organization will first look at the reaction to do the process. Questions will be asked about how the process went and how the individuals feel about the training. Exploring females in management, it is important for the company to gather facts and get reactions on how the individual was treated and how the training process felt. “As an organization it is stated that the cost of employing women in management is far greater than the cost of employing men so it is important that the evaluation process is effective.”(Harvard Business Review, 2011) As an organization we will provide our managers with experiences involving walkthroughs to stores that they are familiar with to test effectiveness of the training. The organization will provide stores consistent with diversity so that a male or female will feel comfortable in their environment. The organization will also test some of the qualities learned in the training by putting individuals in hands on situation that involves what managers do every day in certain situations. Since there have not been many females in higher position such as managers, interactions with other employers will be involved in the......

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Designing and Delivering L&D

...number of current learning interventions, and why they may or may not be suitable for implementation at Whitstable Party Company. Alongside learning, evaluation; being able to measure return on investment, is key in ascertaining the effectiveness of learning methods in the business. Therefore, a number of evaluation models ad strategies will also be considered. Overall, this report seeks to provide balanced guidance on learning methods, and suggestions as to how their effectiveness can be measured at Whitstable Party Company. Question One There are many different methods of current learning in business that can be considered and mixed to ensure learning is kept alive in the work place. The ‘learning’ method that was used in the management development programme can be described as ‘training’. It was instructor led, based on set material, and the purpose was to teach skills and begin to lead a change in the behaviour of the management team. The target audience are the management team, and fall into the category ‘adult learners’. According to Malcolm Knowles, the following should be considered when designing learning events for adult learners:- • Make clear the reason for the learning • Experience provides the basis for learning new activities • Responsibility for decisions and involvement in planning and evaluation • Learning must be relevant to work or life • Problem centred rather than content-oriented • Internal rather than external motivators......

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