Exp. 30 Postlab

docx

School

Rensselaer Polytechnic Institute *

*We aren’t endorsed by this school

Course

2240

Subject

Chemistry

Date

Feb 20, 2024

Type

docx

Pages

Uploaded by ElderRook558

Isaac Crane Section 1 Experiment 30 Synthesis of Triphenylmethanol 2/5/2024 Data and Results: Describe the physical appearance and state of your product (e.g. white crystalline solid). The first week of lab gave a product, which was separated into 2 layers, the organic and the aqueous layer which would be separated in week 2. There was some crystalline solid within the flask that was dissolved with extra ether. Week 2 gave a product, of which was a white crystalline solid which was obtained after recrystallization. .  Recalculate the theoretical yield based on the actual mass of benzophenone used (show calculations). Mass Benzophenone=3.67g 3.67x(1mol Bromobenzene/182.2)x(1mol Triphenylmethanol/1mol bromobenzene)x(260.3/1) Theoretical yield= 5.202g Report the actual mass and percentage yield of your product (show calculations). Mass=0.202g (0.202/5.202) *100=3.89% Percent yield=3.89% yield Report your measured melting point/range and the literature melting point of the product. MP lit= 161-164 degrees Celsius MP Data= 130-148 degrees Celsius  Attach the IR spectrum of your product to your postlab report. On the spectrum, be sure to label the diagnostic absorption bands, showing the type of bond vibration involved (for example, sp 2 C-H stretch , C-O stretch , etc.). Also, draw the structure of the product on your spectrum. Sp2C-H ` Sp2 C-C O-H C-O C-O Isaac Crane

Section 1 Experiment 30 Synthesis of Triphenylmethanol 2/5/2024 Discussion and Conclusions: Did you achieve the objective of the experiment? The objective of this experiment was to prepare triphenylmethanol from bromobenzene by making a Grignard, consuming it, and then adding water. After this the product was separated using a separatory funnel and gravity filtration and purified using rotational evaporation, vacuum filtration and recrystallization and analyzed the solution by determining the melting point and acquiring the IR spectra of the product. Therefore, based on the objective, the experiment was successful and Triphenylmethanol should have been obtained, and based on the experiment done itself, the result was triphenylmethanol, however it did have a low melting point which meant that the product had a fair number of impurities. Discuss whether the measured melting point/range confirms the identity of the product and can be used as evidence of purity. Compare the measured melting point/range and the literature melting point and draw a conclusion about the purity of the sample. The melting point range of the product was 130-148C which is well below the lit value of 160-164C. You could possibly use this to identify the product since there are no unknowns in the experiment, however you can use the melting point given to assess the purity of the sample. Because the MP was lower than the lit value then there are impurities driving the melting point down. So, the product received is pure, but it does have impurities within it. The IR spectrum showed a determination to the final product being triphenylmethanol. There was a clear O-H peak at 3457 cm-1 which is consistent with an alcohol product. The triphenylmethanol consists of 3 benzene rings resulting in the sp2 bonded carbons shown around 3061 and 3029 cm 1. There should also be C-C sp2 bonds from the benzene which are shown in the IR spectrum at 1597 to 1444 cm-1. The IR spectra also shows C-O peaks around 1154 cm-1, which is consistent with triphenylmethanol. Therefore, based on the IR spectra the product is consistent with triphenylmethanol and confirms its identity.  Compare the IR spectrum of your product with the IR spectra of the starting materials in Figure 30.1 on page 274 and describe the evidence indicating that the expected reaction has taken place. Comparing the experimental IR spectra with the spectra in the textbook shows that they are similar. For example, the peak on the bromobenzene IR at 3064 and the 1447 peak are similar to the peaks are the same areas on the benzophenone spectra.

Section 1 Experiment 30 Synthesis of Triphenylmethanol 2/5/2024 Discuss the product yield and purity and any possible sources of error. For example, if you obtained an impure product or the yield was very low, please try to propose possible reasons for these outcomes. Also, in your opinion, how would you improve the outcome, if you were to repeat this experiment? The product from the experiment had an MP of 130-148 C which indicates that there may have been significant impurities in it since the melting point of Triphenylmethanol is 160 to 164 degrees C. As well as this the yield was extremely small at 0.202 grams. Sources of error that would have caused this could be water and/or acetone could have gotten into the reaction flask which would make a different product and impact the impurity. As well as this, not cleaning the glassware toughly before the experiment could leave residual products from another lab which would be impurities in this lab. Water could also be introduced via the air which starts the reaction to make impurities and not drying the product long enough would artificially heighten the mass of the product. Errors that would cause the low yield would be loss in product by letting it boil off during the recrystallization step. As well as this human error like spillage, and not checking equipment can cause losses in product in the end. Other errors that could have appeared are, losses of product from the gravity filtration, losses when using the separatory funnel, and/or losses due to the storing of the reaction flask for about a week. If I were to do the experiment again, then I would pay closer attention during the recrystallization step to assure that there is minimal to no loss via boiling. As well as this, making sure that all equipment is functioning properly before attempting that step would result in less loss of product. Along with this, taking more care to make sure no water or acetone is introduced to the reaction mixture by any means would make the impurities less which would increase the MP. As well as this, being more careful when taking out the layers in the separatory funnel would increase the yield for the product. References: Book John.w. Lehman, Multiscale Operational Chemistry a problem-solving approach to the lab, Massachusetts; Pearson learning solutions,2021.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version