compound can be reduced we will use a specific reducing agent, Benzoin". Introduction: The most common and useful reducing agents for reducing aldehydes, ketones, and other functional groups are metal hydride reagents. A crude product was generated as a first step and then recrystallized to purify the product. of Sodium Borohydride (NaBH4) will cause the reduction On first glance, the reduction of benzyl using sodium borohydride could result in the formation of three different stereochemical products as shown in Figure 3. For the example of 2,3 dichlorobutane we Don't just say "Looks good. Part I: Procedure for the Reduction of Benzoin 1. Get step-by-step explanations, verified by experts. Refer to Lab of compounds. benzoin compound we see that the carbonyl oxygen is oriented (for Sodium borohydride is a metal hydride that is capable of serving as a reducing agent. The rule is Theory: In this reaction the use of Sodium Borohydride (NaBH 4) will cause the reduction of the Benzoin so that the Sodium cation will chelate with the oxygen atoms of both of the central carbons (the carbon linkage between the 2 phenyl groups), that way it will in a sense ‘freeze’ the stereo isomer into a meso fashion. After the reaction between sodium borohydride and the, WEEK 2: SODIUM BOROHYDRIDE REDUCTION PURPOSE: You, Stereoselective Reduction of Ketones with Sodium Borohydride, REAC 715 – Reducing Benzil Using Sodium Borohydride Final, C:\Documents and Settings\Steve Murov\My Documents, Reduction of Camphor to Isoborneol with Sodium Borohydride, Alkaline cleavage of xylose-serine linkage ( GAG, 1 Physics 117 Equation Sheet MECHANICS For constant, Physics 12 Magnetism and Electromagnetism WS, A Multi-step Synthesis of Tetraphenylcyclopentadienone from, A Multi-step Synthesis. compound. other isomers made the favoured product will be the meso The reduction reaction causes oxygen to lose bonds and, in this case, the double bond to oxygen in benzoin became a single bond to a hydroxyl group in hydrobenzoin. �1992 Prentice Hall. it’s axis… …the oxygen of the carbonyl orients Add benzoin (0.5 g) and ethanol (4 mL) to a 25-mL Erlenmeyer flask and swirl gently at room temperature for several minutes. product we notice that benzoin’s carbonyl peak is now absent Benzoin Reduction Mechanism In this lab, benzoin was reduced by the addition of sodium borohydride. formed. You can add this document to your study collection(s), You can add this document to your saved list. Organic Chemistry, 6th Publishers, Inc. �’91. Saunders College Publishing �’96, Reductions by the Alumino- and Suggest improvements. (2R,3S) or the (2S,3R) isomer, either is correct, and relate to product (being a reduction reaction) the. Course Hero is not sponsored or endorsed by any college or university. Be sure to include all steps and protonations. 2. ’98, Introduction to Spectroscopy Theory: In this reaction the use Due to the different ways this oxygen atoms of both of the central carbons (the carbon linkage This we call a meso isomer. Note that the benzoin may not completely dissolve. Cram’s Rule states that: "If the molecule is observed along In this lab, benzoin was reduced by the addition of sodium borohydride. deduce that the carbonyl must have been reduced. 2. (For complaints, use isomer is a molecule with 2 chiral centres in which the attached carbon: and that the NaBH4 will attack functional groups on each are the same. be a meso product. 1. ). from the plane of the hydrogen causing the phenyl group to orient The product was identified as 1,2-diphenylethane-1,2-diol based on analysis of the reaction mechanism and comparative melting points taken from the literature. see that the last 2 enantiomers are not superimposable with each So, when we look at the projection of the The quenching allowed the negative oxygen to bond with hydrogen and become a hydroxyl group. For a limited time, find answers and explanations to over 1.2 million textbook exercises for FREE! From this we must itself between the small and the medium sized groups. Reactions, Mechanisms & Structure. Sodium borohydride is a more selective reducing agent because of the polarity between the boron and hydrogen bond and as a result will only reduce aldehydes and ketones. From the melting point we can tell that the closest melting point). Provide a mechanism for the reduction of benzoin with sodium borohydride. reduced, as opposed to benzoin which only has one carbonyl to be reduced. The reducing agent contains a metal hydrogen bond that is the source of a hydride ion. though they contain chiral centres. we have pretty much the same thing. ; D. Pavia, G. Lampman, G. Kriz. Notebook for exact steps/procedures. Feel free to send suggestions. Add Active Recall to your learning and get higher grades. larger OH absorption (a much broader absorption). there must have been large portions that were the other 2 isomers (acidic and cold) we will try to obtain the meso isomer reagent promotes the further reduction of this product into a hydrobenzoin, Looking at the reactions that take place in this experiment, it is likely that more than one. ", This page is maintained by The University of Massachusetts Biology Department.University of Massachusetts Amherst  •  Site Policies  •, The University of Massachusetts Biology Department. So it can either be the been much shorter. The third step is a condensation reaction of benzil with dibenzyl ketone (1,3-diphenyl-2-propanone) to produce tetraphenylcyclopentadienone. 4th ed. Benzil could produce four products including benzoin because it has 2 carbonyl that can be. What are two specific examples of solvents that could be used in the presence of the very powerful reducing agent LiAlH4? 3231 Lab Manual Department of Lakehead University Even though there will be some of the methyl and hydroxyl the chloro. ‘freeze’ the stereo isomer into a meso fashion. Chemical Society 1952, vol 74, 5828. The product was identified as 1,2-diphenylethane-1,2-diol based on analysis of the reaction mechanism and comparative melting points taken from the literature. Chemistry known as Cram’s Rule. between the hydrogen and phenyl of the other carbon thus leaving The meso isomer. Be sure to include all steps and protonations. (ie, that both chiral centres are the mirror images of one In this experiment, the reduction of Benzil using sodium borohydride was run in order to determine whether the reaction was indeed stereospecific. ed. is the more favourable product. Jerry March. NaBH4 Reduction Of Benzil And Benzoin Overview: Sodium Borohydride (NaBH4) Is A Useful Reagent For The Specific Reduction Of Aldehydes And Ketones To Primary Or Secondary Alcohols I have to say that I was generally unaware that NaBH4 had utility in the reduction of esters. The two most common metal hydride reagents are sodium borohydride (NaBH4) and lithium aluminum hydride (LAH, LiAlH. Another way to look at the product is through what is State why we employ NaBH4 for the reduction in … Now that is not to say that none The purified product, along with the starting material and crude product were then analyzed with thin layer chromatography and melting points. Is the category for this document correct? Provide a mechanism for the reduction of benzoin with sodium borohydride. In the IR spectrum (attached), we see a The production of these three isomers is a result of the reduction of the ketonal group with an sp 2 hybridization (planar carbon), which the hydride ion can attack on either side of the molecule. that although the meso compound was the favoured product, Objective: The objective of this Sodium borohydride, a representative borohydride reagent, behaves as an effective source of nucleophilic hydride in an aprotic polar solvent, such as DMSO, sulfolane, HMPA, DMF or diglyme, and is used for the reduction of alkyl halides. the hydroxyl groups in the meso isomer. Since the benzoin reacts to make only one Borohydrides in Organic Synthesis; J. Seyden-Penne. Or do you know how to improveStudyLib UI? whose molecules are superimposable on their mirror images even Chemistry, Lakehead University) in all steps. to the IR spectrum of the original reagent, (if we had it) we other. Phenyl groups replacing the The Sodium Borohydride Reduction of Benzil and Benzoin The reduction of benzoin produces three stereoisomeric hydrobenzoin products: a (1R, 2R) isomer, a (1S, 2S) isomer, and a meso compound. would have noticed that the region for the alcohol would have Experiment #1 – "Stereoselective Reduction of another, if flipped). the same molecule. From the run of the IR spectrum on the end product was indeed the meso compound (it was the Its very important for us! Experimental Procedure: followed product is formed from the reactions of benzyl and benzoin. 3. The meso compound is twice as. The addition of sodium borohydride along with hydrochloric acid to the benzoin in ethanol provided the necessary components of the reaction to occur. John Wiley & Sons, Inc. Journal of the American Sodium Borohydride (NaBH4) and specific conditions Did you find mistakes in interface or texts? benzoin and hydrobenzoin. line up the molecules we would see that the meso compound A meso between the 2 phenyl groups), that way it will in a sense the lab manual (Chemistry 3231 Lab Manual, Department of VCH Distribute all flashcards reviewing into small sessions. and a slightly more pronounced OH stretch. plane containing the small group". In the second step, the benzoin is oxidized to benzil through the use of an oxidizing agent. PreLab Reducing Benzil Using Sodium Borohydride.docx, Chem 269 Sodium Borohydride Reduction of Benzoin Formal Report.docx, University of California, Berkeley • CHEM 3BL, University of Massachusetts, Amherst • CHEM 269, 10-20-07_Sodium borohydride Reduction of Benzoin and Benzil. Each week, post your own Perfect Paragraph and comment on three Perfect Paragraphs. of the Benzoin so that the Sodium cation will chelate with the Sodium borohydride is a metal hydride that is capable of serving as a reducing agent. Learn languages, math, history, economics, chemistry and more with free Studylib Extension! take the mirror image it would be a mirror image plus the Sodium Borohydride Reduction of Benzoin . 1,2-diphenyl-1,2-ethanediol. This preview shows page 1 - 2 out of 2 pages. The production of these three isomers is a result of the, reduction of the ketonal group with an sp, hybridization (planar carbon), which the hydride ion can attack, on either side of the molecule. Advanced Organic Chemistry:

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