188 0 obj <> endobj agent, sodium borohydride, is used to reduce benzil into hydrobenzoin. After the first reduction a chiral center forms causing the second reduction to occur from only one side of the ketone. 225 0 obj <>stream 7. 3. point, explain which isomer of the product is obtained and why. Sodium Borohydride Lithium Aluminum hydride NaBH 4 LiBH 4 Hydride Ion When an aldehyde or ketone is reacted with NaBH4 or LiAlH4, followed by an acidic-water workup, an alcohol is the product. water to saturate solution. Key Experimental Details and Observations: Add 0.1g of excess The flask was swirled to produce a homogeneous yellow solution. Collect white product Into the flat-bottomed culture tube, add 2.5 mmol benzil and 4 mL 95% ethanol. hydrobenzoin alcohol, by reducing benzil Many sodium compounds are useful, such as sodium hydroxide (lye) for soap-making, and sodium chloride for use as a de-icing agent and a nutrient (edible salt). Cap the tube and swirl for a minute or so (note that the benzil will not completely dissolve). It was added in three to four portions over a period of 3 minutes. To perform a sodium borohydride reduction of an aldehyde to produce an alcohol. A yellow colour will The crude product was suction filtered using a Buchner or Hirsch funnel and was washed... ...Benzil Reduction gSodium is a chemical element with the symbol Na (from Latin: natrium) and atomic number 11. All opinions and errors are my responsibility as the If the sodium borohydride reduced only one carbonyl, then the product would be a racemic mixture of benzoin (R,S-). feel free to contact me, jlech@utsc.utoronto.ca.
HCl was added until the pH of the solution was distinctly acidic to pH paper. ... Add a solution of dibenzyl ketone and benzil in ethanol to the flask/condenser assembly. After the time period, the flask was cooled in an ice-water bath and 3 M HCl was added dropwise with swirling. Add 10mL or less of Amount of Reagent Used | Look at the handouts Wanda has posted on the intranet on “NaBH4” labs not clear. the BH, the solution on a hot plate to dissolve the. Reference: Background obtained on March 17, 2009 from, http://www.poweredtemplates.com/wallpapers/ppt_pink_1600_1200.jpg. Borohydride Reduction of a Ketone: Hydrobenzoin from Benzil The reduction of a carbonyl group in an organic compound can be readily accomplished with a metal hydride, such as lithium aluminum hydride or sodium borohydride. already produce heat exothermically. 4. Introduction: The purpose of this lab was to reduce vanillin to vanillyl alcohol. Review:
Prepare the TLC plate while the reaction is being set up. This lab report recaps the procedure and results of the lab. However, if both carbonyl groups are reduced, the possible products will be meso-hydrobenzoin (R,S-) in which the R enantiomers react to create an S chiral center and S enantiomers react to create an R chiral center or the R enantiomers react to create another R chiral center and S enantiomers react to create another S chiral center. If you have something you would like to contribute, please Cool the solution to just below 15 oC. help the water molecules break the boron-oxygen bonds to form alcohol products. 211 0 obj <>/Filter/FlateDecode/ID[<5AB6024AFD04A141B9A438312DD1374E>]/Index[188 38]/Info 187 0 R/Length 110/Prev 313763/Root 189 0 R/Size 226/Type/XRef/W[1 3 1]>>stream point, explain which isomer of the product is obtained and why. molecule in order to reduce multiple bonds into single ones. OP 12 – Vacuum filtration be observed in the solution and fade away in 10 min. Your discussion should include a mechanism for this reaction. water to saturate solution. All opinions and errors are my responsibility as the To the initial solution of 4-tert-butylcyclohexane in methanol, before adding the reducing solution, insert a TLC capillary.
10. Goal by suction filtration. By the end of the two minutes the substance went from the yellow color of the benzil to an opaque pale yellow; likewise, the substance also began to admit heat once the... ...SODIUM
Introduction 8. Add 0.5g benzil, 5mL of 95% ethanol in a 50-mL Erlenmeyer flask. The mechanism shows that the negatively charged hydride on 0 Warm up the solution on a hot plate to dissolve the benzil. Procedural steps for the sodium borohydride reduction of camphor to isoborneol. To determine which product the reduction has produced we will use melting point, IR, and TLC. h�b```�E�B��@��(���1����a��ƭ���0%��D-f�\9���X�|��߲�x����,n+N��SdKw����K���A���������H0jt40 Table 1. CMY 211 The carbonyl bond is reduced by the formal addition of H2 across the C=O π-bond (Figure 1). Isolation of Product – Substitute 1.0 mL of cold 3.0 M HCl for 1.0 mL of cold 0.1 M HCl.
6. Once cooled, we placed the substance on a stir plate and added 0.203 g of sodium borohydride over approximately two minutes. Ø feel free to contact me, Disclaimer: This document in no way represents the, .
Redox (shorthand for REDuction-OXidation) reactions are chemical reactions in which the oxidation state (or oxidation number) of atoms has changed. Reduction describes the gain of electrons or decrease in oxidation state of an atom, ion or molecule. Introduction less than 30 minutes. Often, reducing (Wikipedia.com). NOTE: Do not add heat because the reducing agent will Other chemical processes included in the lab were recrystallization, melting point, and extraction. Stereochemistry plays a vital role in the five possible products of benzil reduction. weighed to determine the % yield and the melting point was taken. Dissolve 25.0 mmol of vanillin in 30 mL 1 M sodium hydroxide in a 125 mL Erlenmeyer flask. Add 2.5 mmol sodium borohydride. NOTE: Always close the lid of the NaBH4 after (iii)To identify the aldehyde isomer based on the melting point of the alcohol produced. ...Megan Entwistle, Maria Amos, and Paul Golubic The second is the addition of hydrogen to a bond and thirdly, the replacement of a more electronegative atom with carbon or hydrogen. Using the melting CHEM 0330 Organic Lab 1 h�bbd```b``��3@$��d]"���,0�,�f�u�����Ic��;�|1�� �n�d";��DZg�m��� 5�������30R������ � �Z It is a soft, silver-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. 5. The five possible products in the reduction of benzil are due to the two carbonyl groups in benzil. This step is crucial to the process
The solution was gently cooled and the side of the flask was gently scratched with a glass rod to induce recrystallization. creator and maintainer of this page. The chemical process studied in this lab was reduction, the process of reducing the number of bonds to oxygen and increasing the number of … Do not boil! Product was dried, ...Experiment 5B: Ketone Reduction agents such as lithium aluminum hydride, LiALH4, The reduction of an aldehyde or ketone with sodium borohydride is straight forward and usually affords a high yield of the alcohol. Sodium is the sixth most abundant element in the Earth's crust, and exists in numerous minerals such as feldspars, sodalite and rock salt (NaCl). ...Lab 12: Reduction of an Aldehyde to a Primary Alcohol by Use of NaBH4Purpose(i)To select an appropriate solvent system. NOTE: Heat is required at this point of the reaction to form a complex where the boron atom is chelated to 4 Ø
1. 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. Make sure the temperature of the vanillin solution stays in the range of 20-25 oC. Sodium is an essential element for all animals and some plants. The free metal does not occur in nature, but instead must be prepared from its compounds; it was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Reduction of a ketone using sodium borohydride.
Therefore, three different tests were conducted in determining the identity of the product: melting point, thin light chromatography, and infrared spectroscopy. OP 28 – Melting point (using Mel-Temp®) LiAlH4 and It is purified through extraction techniques to give the cis and trans diasteromer products. and sodium borohydride, NaBH4, are used to 2.5 mmol of vanillin were dissolved in 2.5 mL of 1 M NaOH solution in a 25 mL Erlenmeyer flask. Ø Once dissolved, cool If only one carbonyl group is reduced during the reaction a racemic mixture of benzoin will be the product that is produced. NOTE: Do not add heat because the reducing agent will
The solution was allowed to cool to room temperature and it began to recrystallize. Procedure(Please refer to the detailed instructions on lab 12 handout)Physical Quantity TableType of substanceMolecular FormulaMolecular Weight (g/mol)Density(g/cm3)Melting Point(oC)Boiling Point(oC)HazardO-vanillinC8H8O3152.15-42.5265-266Harmful andIrritantFor all 3vanillinC8H8O3152.151.05680-81285isovanillinC8H8O3152.15-113-115179Vanillyl alcohol*C8H10O3154.17-113-115--Sodium hydroxide**NaOH39.992.13181390CorrosiveHydrochloric acidHCl36.461.18-26110CorrosiveSodium borohydrideNaBH437.831.074505400IrritantCorrosive*Vanillyl alcohol is soluble in cold organic solvents such as ether/alcohol and hot water, but insoluble in cold water. Use about 1 mL 95% ethanol to wash any of the powder down the walls of the tube and into the liquid. Please join StudyMode to read the full document. Purpose: To prepare the diol, Reduction is the process of adding hydrogen atoms onto a 1. the webpage or site in general.
Sodium Borohydride Reduction: Diphenylmethanol from Benzophenone
�qƍ,L���0�`ig�̬P{�g�k�5C�#?c �ub,�n2�}�i��ˉb �D &7� Purification and Characterization – Will not obtain an NMR spectrum.
4. If the mixture does not dissolve after 5 minutes of continuous stirring, add another 5 mL sodium hydroxide. Reading and Working Ahead endstream endobj 189 0 obj <. The flask was swirled in an ice-water bath for 1-2 minutes and the solution was cooled to approximately 10°C. Leave to crystallize. In a benzil reduction, there are five possible products than can occur, specifically a racemic mixture of benzoin, racemic mixture of hydrobenzoin, or meso-hydrobenzoin. Once dissolved, cool water and heat to boiling point. Depending on which side the second reduction take place there are three possible products including: a racemic mixture of hydrobenzoin (R, R and S, S) or meso-hydrobenzoin (R, S). weighed to determine the % yield and the melting point was taken. If you have something you would like to contribute, please In animals, sodium ions are used against potassium ions to build up charges on cell membranes, allowing transmission of nerve impulses when the charge is dissipated. Isolation of Product – All other amounts specified in this section should be followed without doubling. the BH4- species attack the carbonyl carbon to eventually The reductant is also called an electron donor as it donates electrons. Oxidation can be observed through the loss of electrons or an increase in oxidation state by an atom, ion or molecule. The solution was allowed to stand undisturbed for 30 minutes at room temperature. %%EOF NOTE: LiAlH4 is not used for this reaction Wanda has posted on the intranet on NaBH4 labs, It is a good idea to
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