Ochem 2 Prelab 8 PDF

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Ochem 2 Prelab 8...

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Introduction The majority of the methods that have been used thus far to create alkenes have involved simple E1/E2 reactions. The witting reaction is another way to create an alkene. The witting reaction involves a compound called a Ylide and a carbonyl group. In our experiment, NaOH is used to deprotonate benzyltriphenylphosphonium chloride and form the Ylide. The Ylide is then reacted with 9-Anthracene to form Trans-9-(2-phenylethenyl)anthracene. The solvent in this week’s lab isn’t the typical diethyl ether. The Ylide is very hydrophilic and will thus readily dissolve in water while the aldehyde is hydrophobic and thus not soluble in water. The salt will dissolve in the water (aqueous) layer but will still be able to react with the aldehyde in the organic layer at the phase barrier between the layers; the reaction mixture must be stirred constantly to maximize the surface area of reaction. Table of Reagents Structure/Name

Molecular Weight Benzyltriphenylphosphonium 388.86 chloride g/mol

Meltin g Point 337°C

Boiling Point N/A

Densit y N/A

MSDS

9-Anthraldehyde

206.24 g/mol

103105°C

N/A

N/A

- skin and eye irritant -Respiratory tract irritant -Extremely hazardous in case of ingestion or inhalation -Skin permeator -Toxic in case of ingestion or skin contact -Acute Oral toxicity

Trans-9-(2phenylethenyl)anthracene

280.37 g/mol

130133°C

N/A

N/A

- skin and eye irritant -Respiratory tract irritant

-skin and eye irritant -Extremely hazardous in case of ingestion or inhalation -Skin permeator -Toxic in case of ingestion or skin contact -Mutagenic to mammalian somatic cells -Acute Oral toxicity

-Extremely hazardous in case of ingestion or inhalation -Skin permeator -Acute Oral toxicity - Very hazardous in case of ingestion or inhalation -Skin and eye irritant and corroder -Skin permeator -Toxic in case of inhalation or ingestion -Classified 2B Carcinogen for humans - toxic to lungs, the nervous system, liver, mucous membranes, central nervous system -Repeated or prolonged exposure may lead to target organ damage -Acute toxicity of Vapor -Acute Oral Toxicity N/A

Methylene Chloride

84.93 g/mol

N/A

39.75° C

1.3226 g/cm3

Water

18.01 g/mol

N/A

100 °C

.999 g/cm3

1-Propanol

60.1 g/mol N/A

97.22°C

.803 g/cm3

-Skin and eye irritant -Skin permeator -Hazardous in case of ingestion and inhalation -Acute oral toxicity -Acute dermal toxicity -Acute vapor toxicity

Sodium Hydroxide

40.0 g/mol 323°C

N/A

N/A

-Very hazardous in case of ingestion or inhalation -Skin permeator -Skin and eye irritant and corroder -Eye contact can result in corneal damage or

blindness -Inhalation of dust will produce irritation to gastrointestinal or respiratory tract -Severe over-exposure can produce lung damage, choking, unconsciousness or death -Mutagenic for mammalian somatic cells -may be toxic to mucous membranes, upper respiratory tract, skin, eyes -Repeated or prolonged exposure may lead to target organ damage -Acute Oral toxicity

Calcium Chloride

110.99 g/mol

772°C

N/A

N/A

-skin and eye irritant -hazardous in case of ingestion or inhalation -skin permeator -mutagenic for mammalian somatic cells -mutagenic for bacteria or yeast -may be toxic to heart and cardiovascular system -repeated or prolonged exposure may result in target organ damage -acute oral toxicity -may be tumorigenic

Safety  All MSDS data in the Table of Reagents  Lab gloves and goggles must be worn at all times  Benzyltriphenylphosphonium chloride, 9-anthraldehyde, and methylene chloride are highly toxic  Sodium hydroxide is highly caustic  Methylene chloride is highly flammable  Ensure proper positioning and functioning of snorkel  Avoid inhaling any fumes or ingesting and reagent residue Procedure 1. Add 1.0 g benzyltriphenylphosphonium chloride, .590 g 9-anthraldehyde and a spin vane to clean 10 ml round bottomed flask 2. Add 2.5 mL methylene chloride and begin to slowly stir 3. Add 1.3 mL 50% NaOH over a three minute period 4. Allow the flask to stir at room temperature for an additional 30 minutes

a. Monitor the spin vane to make sure the reaction mixture is stirring the entire time 5. Remove the spin vane and carefully transfer the contents of the 10 mL round bottomed flask to a separatory funnel 6. Rinse the round bottomed flask with 5 mL methylene chloride and transfer contents into separatory funnel 7. Rinse the 10 mL round bottomed flask again with 5 mL deionized water and add contents to separatory funnel 8. Identify the two layers based on density values of reagents 9. Drain the organic layer into a clean, dry 25 mL Erlenmeyer flask 10. Extract the remaining aqueous layer with a 10 mL portion of methylene chloride 11. Drain and collect this extract in the 25 mL Erlenmeyer flask a. Drain off the aqueous layer and save it till the end of the experiment as a cautionary measure 12. Add an appropriate amount of calcium chloride pellets to remove any remaining water a. Exact amount of calcium chloride needed will vary based on volume of water in the flask 13. Once the solution is dry, decant into a clean, dry 50 mL round bottomed flask 14. Construct a simple distillation apparatus and use it to separate the methylene chloride form the crude product a. Be careful not to distill the product to dryness 15. Remove the heating mantle and allow the apparatus to cool to room temperature 16. Recrystallize the product using a minimal amount of 1-propanol 17. Use an ice water bath to aid in the final precipitation of the crystals 18. Collect the purified Trans-9-(2-phenylethenyl)anthracene via suction filtration a. Continue to pull air for an additional 5 minutes after crystals are collected 19. Transfer final product onto watch glass and place in a drying oven for an additional 5 minutes 20. Determine final mass and melting point range of the product 21. Obtain an IR spectra of the product with the help of your TA

Mechanism

Balanced Equation...