Lab report 2 - chem 2220 PDF

Preview

Summary

chem 2220...

Description

1A) Metal hydrides such as NaBH 4 ,LiBH 4 can be used to reduce a number of organic functional groups to more useful functional groups(1). Sodium borohydride is used to reduce ketones and aldehyde to alcohol(2). It is known as a mild and selective reducing agent as in solution it reduces aldehyde and ketone rapidly,ester slowly,while other carbonyl containing functional groups do not react(3). For experiment 2, Sodium borohydride was used to reduce benzil as benzil is alpha-diketone(4). Benzil(0.41g) and 95% ethanol(1ml) were mixed in a flask in ice bath and then Sodium borohydride(0.078g) was dissolved in 95% ethanol(3ml) and added dropwise to the solution as it reacts violently when added to the mixture too quickly and produces lot of heat(5). Flask is then removed from the ice bath with occasional stirring and then water(4ml) was added to it and boiled and then additional water (12ml) was added to it until it turned cloudy. Solution was then cooled to form crystals and by using vacuum filtration white crystals(0.29g) were dried and obtained and melting point and IR of the crystals were obtained. 2A)

General concept and idea about the peer review process was found online (6) andhe flowchart as made using chem draw. 3A) Experiment 2: To identify and determine the purity of experiment 2 product , IR and melting point was taken. Firstly, the melting point recorded for the product was between 135.9℃-137.5℃ .The crystals started showing changes around 135.9℃ and then completely melted around 137.5℃ . This melting point range was close to the melting point range of hydrobenzoin i.e. 134℃-136℃ (7), instead of the melting point of benzoin i.e.137℃(8). The experimental melting point range was close to the literature melting point range of hydrobenzoin and since there is no large difference in the melting points , we can assume that the product made is pure.Secondly, benzoin has one carbonyl and one OH group while hydrobenzoin has no carbonyl group instead has two OH group present.In the IR spectrum , there was two peaks observed in 3300cm − 1 , which shows O-H stretch. Two peaks indicate the presence of two OH groups. There was no peak for carbonyl group observed in the IR spectrum , which clearly gave us evidence that the product obtained from experiment 2 was hydrobenzoin.

Experiment 3: To determine the purity of the product, ethyl trans-cinnamate, IR was taken. In the IR spectrum, at 2736-2817cm− 1 , there was a weak aldehyde peak(2 peaks) observed , indicating the reactant benzaldehyde is not present in ethyl trans-cinnamate. At 1697cm − 1 , a strong C=O peak was seen and at 1201cm − 1 , a strong C-O peak was also observed . All these groups were present in ethyl trans-cinnamate,indicating the the final product made from experiment 3 was pure. All IR peaks were identified from lab manual (9) Table 1: Melting point (Experiment 2) Compound

Experimental melting point(℃)

Unknown sample

135.9℃-137.5℃

Literature melting point (℃) -

Reference 10

Benzoin

-

137℃

11

Hydrobenzoin

-

134℃-136℃

12

Table 2: IR spectrum (Experiment 2) Wavenumber (cm − 1)

Strength of band

Assignment

3300

medium,wide

O-H bond

2899

medium,narrow

C-H alkanes

1494

medium,narrow

Aromatic C

1019

strong,narrow

C-O alcohols

Table 3:IR spectrum of ethyl_trans-cinnamate (Experiment 3) Wavenumber (cm − 1 )

Strength of band

Assignment

2736-2817

weak

Aldehyde ( two peaks)

1697

Strong,narrow

C=O

1596

medium,narrow

Aromatic C

1201

Strong,narrow

C-O

All IR spectrum peaks identified from lab manual (13) 4A) Mechanism for experiment 2: Benzil reduced to hydrobenzoin using sodium borohydride :

Mechanism for experiment 3: Synthesis of ethyl trans-cinnamate under claisen condensation conditions

Mechanisms were drawn using chem draw . Textbook was referred for help with mechanisms. (14)

Reference

1) Horace Luong,university of manitoba, 2020, Chem 2220: Introductory organic chemistry 2 reactivity and synthesis. 2) Horace Luong,university of manitoba, 2020, Chem 2220: Introductory organic chemistry 2 reactivity and synthesis. 3) Horace Luong,university of manitoba, 2020, Chem 2220: Introductory organic chemistry 2 reactivity and synthesis. 4) National Center for Biotechnology Information. PubChem Database. Benzil,, https://pubchem.ncbi.nlm.nih.gov/compound/Benzil . 5) Wong.Y.(2018,November 17) https://www.researchgate.net/post/Why_is_an_ice_water_bath_needed_in_sodium_boroh ydride_and_silver_nitrate_reaction_to_produce_silver_nanoparticles 6) The Peer Review Process. (n.d.). Author Services | Wiley. https://authorservices.wiley.com/Reviewers/journal-reviewers/what-is-peer-review/the-pe er-review-process.html 7) Lab Equipment and Lab Supplies | Fisher Scientific. https://www.fishersci.com/shop/products/meso-hydrobenzoin-99/AAB2394606 8) National Center for Biotechnology Information. PubChem Database. Benzoin, CID=8400, https://pubchem.ncbi.nlm.nih.gov/compound/Benzoin (accessed on Mar. 3, 2020) 9) Horace Luong,university of manitoba, 2020, Chem 2220: Introductory organic chemistry 2 reactivity and synthesis. 10) Horace Luong,university of manitoba, 2020, Chem 2220: Introductory organic chemistry 2 reactivity and synthesis.

11) National Center for Biotechnology Information. PubChem Database. Benzoin, CID=8400, https://pubchem.ncbi.nlm.nih.gov/compound/Benzoin (accessed on Mar. 3, 2020) 12) Lab Equipment and Lab Supplies | Fisher Scientific. https://www.fishersci.com/shop/products/meso-hydrobenzoin-99/AAB2394606 13) Horace Luong,university of manitoba, 2020, Chem 2220: Introductory organic chemistry 2 reactivity and synthesis. 14) Klein, D. R. (2017). Organic Chemistry, Loose-Leaf Print Companion. John Wiley & Sons....