Assignment 4 - lab work

lab work

Academic year: 2017/2018

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Thursday 12

The objective for the first part of the experiment was to synthesize hydrobenzoin by reducing benzyl using sodium borohydride. Two hydrobenzoin products were produced: meso- hydrobenzoin and enantiomeric hydrobenzoin. Before the addition of sodium borohydride, benzyl and ethanol produced a neon yellow color; however, with the addition of sodium borohydride, the color disappeared and the solution was clear. This color change was an indicator of the reduction mechanism and that the carbonyl and sodium borohydride joining. This results in a carbonyl group becoming a single bond between C-O. When water was added to the solution while using a steam bath, the solution remained clear and the solids that were added before had disappeared. After recrystallization, white flakes formed. This signified that the hydrolysis of the boron complex was complete and that the desired alcohol had formed. The objective for the second part of the experiment was to synthesize camphor by oxidizing isoborneol using bleach. In a solution of isoborneol and acetic acid, bleach was added which produced a bubbling and pale yellow solution. After 15 minutes, the color disappeared to clear and solids formed. The reason for this formation was because bleach contains an active component of bleach, hypochlorous acid. This solution was then tested on a starch iodine paper and produced a dark blue color indicating excess hypochlorous acid was present and the oxidation mechanism was complete. After obtaining the organic product from separatory funnel, the crude product was obtained through vacuum filtration and then product was purified through sublimation. The pure product was white and shiny flakes. The percent yields for hydrobenzoin and camphor products were 65%, 35%, and 39%, respectively. The yields for both cases were low. For the reduction reaction, the solution may have not been clear enough for product collection; the solution may have needed to be filtered by gravity. For the oxidation reaction, the hypochlorous may have not been in excess and

Thursday 12

the reaction may have not been complete; the starch paper testing may have not been dark enough for the experiment to continue. When heating the reaction with the use of aluminum foil, there was still product left on the walls of the flask and could not be scraped off. For both experiments, product loss could be due to transforming product from flask to flask. Product may have been stuck to the flask and could not be obtained. Along with this, not all the solid was cleaned from the funnel leading to product loss. The melting ranges for hydrobenzoin and pure camphor were 137.9-138ºC and 175.3-178ºC, respectively. These ranges indicated that the products obtained were pure and had no impurities. For hydrobenzoin, the melting point indicated it was purely meso-hydrobenzoin since it was within the literature range. Similarities were seen in the IR spectrums. Several of the peaks match with the product IR, such as peaks that indicated aromaticity, such as C-H bonds (~~3030 cm-1), and alkyl C-H (~~2950-2850 cm-1) stretches. This meant that structurally, they were very similar with similar functional groups. However, there are differences. In the product IR, there were peaks indicating aldehyde C=O stretch (1742 cm-1) that was not in the isoborneol. Also, there was an alcohol OH stretch that was broad from the product IR, but in the IR given, the peak was skinny and pointed. Although the shapes of the peaks were different, that functional group was present in both the starting and ending materials. This indicates that there was unreacted isoborneol, which therefore means that sublimation was not effective at purifying the product, although the melting point was still in range with the literature value.

Thursday 12

The objective for the first part of the experiment was to synthesize hydrobenzoin by

reducing benzyl using sodium borohydride. Two hydrobenzoin products were produced: meso-

hydrobenzoin and enantiomeric hydrobenzoin. Before the addition of sodium borohydride,

benzyl and ethanol produced a neon yellow color; however, with the addition of sodium

borohydride, the color disappeared and the solution was clear. This color change was an indicator

of the reduction mechanism and that the carbonyl and sodium borohydride joining. This results in

a carbonyl group becoming a single bond between C-O. When water was added to the solution

while using a steam bath, the solution remained clear and the solids that were added before had

disappeared. After recrystallization, white flakes formed. This signified that the hydrolysis of the

boron complex was complete and that the desired alcohol had formed. The objective for the

second part of the experiment was to synthesize camphor by oxidizing isoborneol using bleach.

In a solution of isoborneol and acetic acid, bleach was added which produced a bubbling and pale

yellow solution. After 15 minutes, the color disappeared to clear and solids formed. The reason

for this formation was because bleach contains an active component of bleach, hypochlorous

acid. This solution was then tested on a starch iodine paper and produced a dark blue color

indicating excess hypochlorous acid was present and the oxidation mechanism was complete.

After obtaining the organic product from separatory funnel, the crude product was obtained

through vacuum filtration and then product was purified through sublimation. The pure product

was white and shiny flakes.

The percent yields for hydrobenzoin and camphor products were 65.8%, 35.1%, and

39.5%, respectively. The yields for both cases were low. For the reduction reaction, the solution

may have not been clear enough for product collection; the solution may have needed to be

Assignment 4 - lab work

Organic Chemistry Lab II (CHEM201401)

Boston College

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