Lab Report 3 Grignard

pdf

School

Nova Southeastern University *

*We aren’t endorsed by this school

Course

ORGANIC CH

Subject

Chemistry

Date

Feb 20, 2024

Type

pdf

Pages

Uploaded by BrigadierAlpacaMaster753

1 Lab Report: Grignard Grignard reagent preparation for Benzoic Acid Synthesis Nicolás Tapia Stoll & Guenevere Coury Professor Beatrix Aukszi & Jarlyn Ramirez 09/26/2023 Introduction: The purpose of the experiment was to prepare the Grignard reagent; phenyl magnesium bromide and use it to synthesize benzoic acid through the reaction with carbon dioxide. The hypothesis for the experiment is that benzoic acid will be produced, resulting in a product of very low pH, and a product with an IR containing a carboxylic acid peak.

2 Results: Mg Ribbon Mass 0.0532g Pre-weighted beaker for Dry Ice Mass 30.7081g Pre-weighted beaker + Dry Ice Mass 32.5646g Dry Ice Mass 1.8565g Pre-weighed Beaker for Product Mass N/A Pre-weighed Beaker + Product Mass N/A Final Product Mass N/A Final Product pH 0-1

3 ?𝑜?𝑒? (?𝑜?) = ?𝑎?? (𝑔) ?𝑜?𝑎? ?𝑎?? (𝑔?𝑜? −1 ) Reaction Equation for First Step: 1C 6 H 5 Br +1Mg → 1C 6 H 5 MgBr Moles used → Mol of C 6 H 5 Br = 6.21𝑔 157𝑔??? −1 = 0.0400?𝑜? Mass of Bromobenzene = 𝐷???𝑖?𝑦 𝑉????? ???? = 1.49𝑔?𝐿 −1 0.240?𝐿 =6.21g (PubChem Bromobenzene) Moles used → Mol of Mg = 0.0532𝑔 24.3𝑔??? −1 = 0.00220?𝑜? hence Mg is limiting Reagent Theoretical Yield = Molar Mass Phenyl magnesium bromide * Moles Mg used Theoretical Yield of Grignard Reagent = 181𝑔?𝑜? −1 × 0.00220?𝑜? = 0.400𝑔 Reaction Equation for Second Step: 1C 6 H 5 MgBr + 1CO 2 → 1C 6 H 5 COO - + HCl → 1C 6 H 5 COOH Moles used → Mol of CO 2 = 1.86g 44𝑔??? −1 = 0.0423?𝑜? Moles used → Mol of C 6 H 5 MgBr = 0.00220?𝑜? hence C 6 H 5 MgBr is limiting Reagent Theoretical Yield of benzoic acid = Molar Mass Benzoic acid * Moles C 6 H 5 MgBr used Theoretical Yield of Final Product = 122𝑔?𝑜? −1 × 0.00220?𝑜? = 0.268𝑔 %Yield of benzoic acid = 𝑌𝑖??? (???????) 𝑇ℎ?????𝑖?𝑎? 𝑦𝑖??? × 100 = 𝑁/𝐴 0.101𝑔 × 100 = ?/𝐴

Your preview ends here

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

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

4 Conclusion: The main experimental findings of the experiment were that the product produced, when tested with a pH paper testing strip gave a red/pinkish color indicating a pH of around 1. A low pH like this was expected as the expected product, benzoic acid, being a carboxylic acid tends to have a very small pH. Unfortunately, this is the only numerical result that could be collected form the experiment due to the fact that on the final step of the experimental procedure, which was the addition of hydrochloric acid to the H 2 O (containing the carboxylate ion). During this step, solid crystals of benzoic acid should have formed in beaker #4, this unfortunately did not happen, despite trying to alter the method by placing the solution on ice, and scarping the bottom of the beaker with a spatula to initiate crystallization. Do to the fact that a final solid product was not produced during the experiment, it was not possible to produce a final product yield mass measurement (resulting in a lack of %yield calculation), as well as it not being possible to run an IR to determine for sure whether the product of benzoic acid was formed. During the experiment there were several observations made, the first being that when having added the hydrochloric acid to beaker #4, the color of the solution containing the benzoic acid changed from clear to a very light yellowish color. Additionally, when stirring the solution in step 13 with a glass rod after having added the dry ice to the solution, bubbling was observed, suggesting a release of small amounts of hydrogen glass during the experiment. In discussion with the fact that no solid final product was produced, some possible reasons for this could have included a failure to exactly separate the water from the ether solution during the extraction’s steps using the separatory funnel. This could

5 have caused impurities like ether to exist in the final product solution inhibiting it from crystalizing when combined with hydrochloric acid. Other reasons could have been caused by instrumental errors or human error such as inaccurate measurements of reactants. Overall, it is hard to determine whether the hypothesis was proved right, since no final product mass, or IR of product was produced from the experiment. Despite this the fact that the final pH of the aqueous product was around 1, does suggest that a carboxylic acid was produced which is a finding that would agree with the hypothesis that benzoic acid would be produced. Bibliography: U.S. National Library of Medicine. (n.d.-a). Bromobenzene. National Center for Biotechnology Information. PubChem Compound Database. https://pubchem.ncbi.nlm.nih.gov/compound/Bromobenzene . Appendix:

6 Standard IR:

Your preview ends here

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