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Chem 234 Lab Final exam with verified answers
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Chem 234 Lab Final exam with verified answers
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Chem 234 Lab Final exam with verified answers1. Synthesis of Benzoic Acid Formula: 1. Bromobenzene with Mg to make grig-
nard
2. React with CO2 to make benzoate
3. Acid workup to make benzoic acid
2. Experimental yield formula: actual/theoretical x 100
3. How to calculate theoretical yield: -Balance equation
Determine limiting reagent (which reagent produces the least moles of product)
-(Moles of limiting reagent used in reaction) x (moles of reagent in equation/moles
of product in equation) = moles of product produced in reaction
-(Moles of product produced) x (molar mass of product) = theoretical yield (in grams)
4. Facts about Grignard: 1. Will act as a base an nucleophile
2. Will always deprotonate OH before attack on ketone
3. Very sensitive to water
5. Characteristic peaks of benzoic acid: broad acid peak 3000-3500
ketone peak: 1710
aromatic ring 1600
sp2 H 3100
6. Apparatus for Benzyl Bromide experiment: All equipment was first flame dried
to remove water
- RBF
- Sitr Bar
- Clesean Head ($53 dollar mf i aitn getting my money back)
- Drying tube
7. Why did benzyl bromide experiment need to be dry?: H20 and Gridnard create
,fire
8. Cleasean Head Purpose: Used to allow for the system to be dry, as well as
adding reagents to the system at the same time
9. Purpose of water bath for Benzyl Bromide experiment: Allow for the reaction
to proceed, Grignard are known to be sluggish
10. How to allow for Grignards to react faster?: 1. Grind Mg
2. Add dibromomethane, reacts with metal and cleans surface
3. Add Molecular iodine - cleans sirface of metal (what we did)
11. liquid-liquid extraction: Requires two immiscible liquids (aqueous & organic
phase) use separatory funnel; higher density on the bottom; like dissolves like;
organic non-polar compounds will dissolve in organic phase
12. liquid-liquid extraction benzoic acid: 2 layers:
- ether layer in top with unreacted PhBR, Benzene and other reactants
- Lower layer on bottom with benzoic acid, since NaHCO3 turns into benzoate and
moves it to the bottom layer
, 13. Product isolation benzoic acid: Aqueous layer acidificed to obtain crystals of
benzoic acid
- also used to get rid of excess Mg metal
- must use vacuum filtration to remove crystals
14. Safety for Benzoic Acid: Diethyl etheran Bromobenzene dangerous to breath
/ flammible
- all steps must be done under the hood
15. vacuum filtration apparatus: Vacuum source
Glass rod / adaptor
125 mL filter flask
Filter Adaptor
Porsilin Funnel / adaptor
25 mL filter flask
16. Synthesis of Ferrocene: A type of Friedel-Craft Acylation:
1. Acetyl chloride reacts with Aluminum Chloride to form an acylium ion and tetra-
chloroaluminate
2. Ferrocene attacks acylium ion do form mono and bis-diacetylferrocene
* This was separated by thin layer chromatography
17. How to calculate retention factor: distance moved by substance/distance
moved by solvent
18. Purpose of Ferrocene: The electrophile for EAS since it is a metalocene
19. Purpose of Aluminum trichloride: This is th Lewis Acid and the electrophile to
create the acylium ion. Later acts as a base to remove proton from ferrocene
was removed
20. Purpose of Acetyl chloride: Acts as a nucleophile where the Cl
to make acylium ion, attacked by ferrocene to make product
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