O-CHEM LAB FINAL – Flashcards
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Balanced equation for the potassium permanganate oxidation of cyclohexanone to adipic acid
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2HCl + C6H10O + 2KMnO4 --> HOOC(CH2)4COOH + 2MnO2 + 2KCl + 2H2O
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Formula for calculating theoretical yield
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Volume * Density = Mass; Mass/molar mass(1) * Molar Mass (2)
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Formula for calculating percent yield
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Actual/Theoretical * 100%
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Sn1 Reaction mechanism
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R:X --slow-->R(+) + X(-), Nu(-) + R(+) --fast-->Nu:R
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Sn2 Reaction mechanism
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Nu(-) + R:X--->[Nu(-)---R---X(-)] -->Nu:R + X(-)
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Which alkyl halide exhibited color change in ethanolic silver nitrate
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1-chloro-2-butene
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Which alkly halide exhibited a yellow color change in Sodium Iodide
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1-chloro-2-butene
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Which alkyl halide exhibited a white color change in sodium iodide
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2-bromobutane
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Why didn't bromobenzene react in NaI/Ethanolic Silver nitrate?
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Steric hindrance due to benzene ring attached to leaving group.
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Comparison of 1% ethanolic silver solution and 1% silver nitrate in a mix of 50/50 ethanol and water
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50/50 silver nitrate mixture reacted with 2-chlorobutane in 2 minutes while the 1% ethanolic silver solution didn't react within 10 minutes of observation.
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Reactivity of alkyl halides in ethanolic silver nitrate sn1
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2-chloro-2-methylpropane>1-chloro-2-butene>2-bromobutane>1-bromobutane
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Reactivity of alkyl halides in Sodium Iodide in acetone, sn2
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2-bromobutane, 1-bromobutane>1-chloro-2 butene, 1-bromobutane
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What would be the effect of carrying out the sodium iodide in acetone reaction with the alkyl halides using an iodine half as concentrated?
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Since the reaction rate directly depends on the concentration of the nucleophile, the reaction rate would be halved if the concentration of sodium iodide is halved
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The addition of sodium or potassium iodide catalyzes many sn2 reactions of alkyl chlorides or bromides. Explain.
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Because Iodide is a good nucleophile it can react with a molecule to form an alkyl iodide. Once formed, this alkyl iodide can be substituted as either alkyl chlorides or bromides readily because iodine is a great leaving group.
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Reactivity of different reactants in the production of Aspirin
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H2SO4>BF3>Pyridine>Sodium Acetate
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Why not use hydrochloric acid instead of sulfuric acid to catalyze the acetylation of salicylic acid?
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Anhydrous sulfuric acid is a liquid while anhydrous HCl is a gas, which is inconvenient. Also, sulfuric acid has two ionizable protons while HCl only has one.
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bond stretching vibrations with high frequency, short wavelength
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C-H, N-H, O-H
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bond stretching vibrations with low frequency, high wavelength
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C-C,C-O
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Correlation between type of bonding and frequency
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Greater bonds i.e double/triple bonds lead to greater frequencies of vibration
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A nonlinear molecule can undergo how many modes of vibration?
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3n - 6 possible modes of vibration
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Analysis of infrared spectra: O-H
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3600-3400 cm'1
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Analysis of infrared spectra: N-H
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3400-3200 cm'1
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Analysis of infrared spectra: C-H
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3300-3000 cm'1
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Analysis of infrared spectra: C(triple bond)N
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2260-2215 cm'1
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Analysis of infrared spectra: C(triple bond)C
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2150-2100 cm'1
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C=O
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1870-1825 cm'1 and 1790-1765 cm'1
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Fingerprint region
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Peaks to the right (longer wavelength) of 1250 cm'1
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Main reaction in order to convert to adipic acid
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The oxidation of a secondary alcohol to a ketone. The ketone can be oxidized further to the dicarboxylic acid giving adipic acid.
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Permanganate ion is used for what?
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Oxidation of a secondary alcohol to a ketone
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Nitric acid is used for what?
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Oxidizing cyclohexane, cyclohexene, cyclohexanol, and cyclohexanol to adipic acid
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Instead of chromium what do we use?
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hypochlorite
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If too much hypochlorite is used how do we destroy it?
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Excess hypochlorite is easily destroyed with bisulfite; the final product is chloride ion, much less toxic to the environment than Cr(III).
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85% phosphotic acid H3PO4 is an acid catalyst used for what?
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Cyclohexanol to Cyclohexene
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What type of distillation is used for the conversion of cyclohexanol to cyclohexene?
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Fractional distillation.
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Why was toluene added to the top of the fraction column after distillation was complete?
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Because there is lost product in the fractional column so a chaser solvent, which is toluene, is used to retrieve the lost product.
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Racemization of sn1 reactions
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The SN1 reaction proceeds through a planar carbocation. Even if the starting material were chiral, the product would be a 50:50 mixture of enantiomers because the intermediate is planar.
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Sn2 inversion
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The SN2 reaction occurs with inversion of configuration to give a product of the opposite chirality from the starting material.
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Order of sn2 reactivity
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Methyl>Primary>Secondary>Tertiary
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Solvent effects on reactivity
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Protic solvents form hydrogen bonds on the nucleophile in an sn2 reaction
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When does solvents prefer sn2 reactions?
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Polar/aprotic
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Why does aspirin need an acetyl group
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to buffer the stomach pains that occur when ingesting asprin. It is a buffering agent.
