An examination of the you 2 diphenyl 1 2


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To undertake the salt borohydride lowering, 1 . 0g benzoin recently synthesized was combined in a 125mL Erlenmeyer flask with 15mL totally ethanol and 250mg salt borohydride. The flask was stirred on a magnetic stir plate intended for 15min. Following 15 minutes, a thin-layer chromatography (TLC) analysis was performed to check for reaction completeness. The TLC developing step was well prepared using a wide-mouthed capped bottle of wine saturated with 4. 5mL ethyl acetate (2-3mm solvent present in the chamber). A simple solution was prepared with a little bit of the benzoin reactant mixed in acetone. A TLC plate was prepared with a 2mm extended mark manufactured on the extended edge in the plate, 1cm from the bottom. Clean micropipettes were used to place the ingredients, the reaction mixture was noticed at 1/3 the TLC plate size, the benzoin solution was spotted at 2/3 the TLC dish width. The plate was put into the developing chamber, which will remained shut down until solvent rose to 1cm from the top of the plate. Once the solvent reached this height, the plate was taken from the step and the solvent line was immediately marked with a pen. The TLC plate was placed in the fume bonnet for 2-3min for solvent evaporation. A UV light (254nm) was for creation and the spots were outlined with a pencil. Appropriate measurements were taken and the Rf values had been calculated. When the reaction was completed the flask was placed in a 400mL beaker, surrounded by snow, and the reaction mixture was diluted with 15mL dH20. The beaker was stirred using a permanent magnet stir menu while 2mL 6M hydrochloric acid was slowly added, followed by 5mL dH20. The mixture was stirred for an additional 15mn. The medicine was accumulated through cleaner filtration using a Buchner funnel and filtration system paper, and after that washed with 25mL dH20. A small amount of the crude item collected was saved for melting point determination. Recrystallization was not performed. The product was placed on a wrist watch glass of known mass and allowed to dry on the 2-day period.

Activity of the cyclic acetal offshoot was accomplished after the drying out period, 0. 4g in the dried 1, 2-diphenyl-1, 2-ethanediol was included in a 25mL Erlenmeyer flask with 5mL 2, 2-dimethoxypropane and 10mg p-toluenesulfonic chemical p monohydrate. The flask was stirred upon at space temperature intended for 60min. The reaction mixture was poured right into a separatory channel containing 50mL dichloromethane, and then 25mL dH20. The organic phase was drained in the funnel in a clean Erlenmeyer flask. The second extraction was completed, 25mL saturated salt bicarbonate was added to the separatory channel and the organic and natural phase was combined with the 1st organic stage collected. A third extraction was completed with 25mL dH20, after the third organic phase was extracted, the combined organic product was dried with anhydrous magnesium (mg) sulfate intended for 10min. The dried option was filtered into a clean 50mL Erlenmeyer flask of known mass with a conical funnel and filter paper. The product was evaporated within a fume bonnet for a 5-day period. After evaporation was completed, the mass and melting stage of the last product had been determined.

Results and Measurements

Salt Borohydride Decrease (4/4/16)

Benzoin = 1 . 0g

Ethanol = 15mL

Sodium Borohydride = 250mg

Monitoring Reaction by Thin-Layer Chromatography

Rf = DistanceTravelledSPOT/DistanceTravelledSOLVENT

Developing Step: Ethyl Acetate = 4mL

Benzoin Remedy = &lt, 10mg Benzoin Product & 1-2mL Acetone

Plate #1 ” RXN @ 15min

Length Travelled Solvent = 4. 6cm

Distance Travelled RXN Mixture @ 15min sama dengan 0. 2cm

Distance Went Benzoin Option = 1 ) 0cm

Rf (RXN Combination @ 15min) = zero. 043478

Rf (Benzoin Solution) = zero. 2173913


dH20 sama dengan 15mL

6M Hydrochloric Chemical p = 2mL

dH20 = 5mL


dH20 (Wash) = 25mL

one particular, 2-Diphenyl-1, 2-Ethanediol Product

Melting Level = 134-136C

Watch Cup = forty-nine. 77g

View Glass + Product = 50. 3-g

Recrystallized Merchandise = zero. 53g

Synthesis of Cyclic Acetal (4/6/16)

1, 2-Diphenyl-1, 2-Ethanediol sama dengan 0. 4-g

2, 2-Dimethoxypropane = 5mL

p-Toluenesulfonic Acidity Monohydrate = 10mL


Dichloromethane = 50mL

dH20 = 25mL

Saturated Sodium Bicarbonate sama dengan 25mL

dH20 = 25mL

Anhydrous Magnesium (mg) Sulfate sama dengan 5 micro-spatula scoops

Cyclic Acetal Product

Melting Stage = &gt, 90C (DID NOT MELT)

Watch Glass = forty one. 08g

Watch Glass + Product = 41. 57g

Product = 0. 49g

Physical Info

Benzoin (C14H12O2) MW sama dengan 212. three or more g/mol

mp = 137C

you, 2-Diphenyl-1, 2-Ethanediol (C14H14O2) MW = 214. 3 g/mol

mp: meso- = 136-137C

() = 121-122C

Cyclic Acetal of 1, 2-Diphenyl-1, 2-Ethanediol (C17 H18 O2) MW sama dengan 254. 3

mp: meso- = 57-59C

() = 44-46C

Yield Calculations

Theoretical you, 2-Diphenyl-1, 2-Ethanediol

Fresh 1, 2-Diphenyl-1, 2-Ethanediol

Percent Yield, Recrystallized 1, 2-Diphenyl-1, 2-Ethanediol

Assumptive Cyclic Acetal of 1, 2-Diphenyl-1, 2-Ethanediol

Trial and error Cyclic Acetal of 1, 2-Diphenyl-1, 2-Ethanediol

Percent Yield, Cyclic Acetal of 1, 2-Diphenyl-1, 2-Ethanediol

Debate and Conclusion

The synthesis of 1, 2-diphenyl-1, 2-ethanediol through sodium borohydride reduction of benzoin was successfully completed throughout this experiment. The percent produce of the 1, 2-diphenyl-1, 2-ethanediol product was calculated being 52. 09%. The happening of the completed reaction was indicated by simply TLC analysis, the Rf value intended for the reaction mixture and the benzoin reactant were calculated to be 0. 0435 and 0. 2174, respectively. The significant big difference in Rf values advised there was comparatively little, if any, benzoin remaining in the reaction blend. The melting point following the evaporation period was established to be 135-136C. This falls between the known melting factors for the meso- and () stereoisomers, which are 121-122C and 136-137C, respectively, yet , the melting point is a lot closer to the () isomer. The results of the burning point dedication suggest that the 1, 2-diphenyl-1, 2-ethanediol item was composed of relatively pure ()-1, 2-diphenyl-1, 2-ethanediol. The lower yield can be due to the make up of the benzoin reactant of unknown purity, which was produced during a prior experiment.

The activity of the cyclic acetal of 1, 2-diphenyl-1, 2-ethanediol was not finished successfully within this experiment. The percent deliver of the dried out product was calculated to get over fully, which is not conceivable. This was likely caused by the existence of excess harmful particles in the blend due to bad extraction approaches and/or glasses contamination. The melting level determination of the cyclic acetal derivative mentioned that the merchandise contained non-e of the designed cyclic acetal, the product from this experiment was not observed to melt for temperatures achieving 90C, it had been expected to dissolve below 60C. This advises the product obtained is largely consists of unreacted one particular, 2-diphenyl-1, 2-ethanediol, which has a shedding point more than 100C. One particular major problem that occurred within this experiment was your loss of potential product due to a leak, the dichloromethane/water/reaction mixture through the separatory channel was spilled and a mysterious amount with the mixture was lost. A NMR analysis of a cyclic acetal item from the meso- stereoisomer will reveal an individual methyl maximum, while NMR analysis from the cyclic acetal product from your () stereoisomer would reveal two methyl peaks.

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