OChem Lab Midterm Prac

Is 2-substitued pyrrole or 3-substituted pyrrole more favored? Why?

2-substituted, has more resonance forms

Where would you expect the C=O absorption of the aldehyde to show up on the IR spec

Appx 1730cm-1

Intermediate formed during the bromination reaction

Bromonium ion

How does UV-vis asses purity

By noting the presence, or lack thereof, of other large peaks with different lambda values

What determines whether the organic layer will be on top or on bottom

Density

What does the term umpolung mean

Polarity of that carbon has been reversed

What is the role of Sodium borohydride in the reaction that is being performed for the Furfural experiment

Reductant

Intermediate formed during double dehydrobromination reaction

See quiz

Acid hydrolysis of xylan, which is present in corn cobs, produces xylose that will eventually become furfural

True

Melting point must be reported as a range

True

Which of the following would dissolve in aqueous sodium bicarbonate a) P-toluic Acid b) P-tert-butylphenol c) Acetanilide

a) P-toluic Acid

Which of the following would dissolve in aqueous sodium hydroxide a) P-toluic Acid b) P-tert-butylphenol c) Acetanilide

b) P-tert-butylphenol

What is the advantage of using PyHBr3 over liquid Br2 a) PyHBr3 releases bromine in the rxn mixture b) Solid PyHBr3 is safer to handle because it minimizes exposure to vapors of Br2 c) Both A and B d) Neither

c) Both A and B

What is true regarding SN2 mechanisms a) Proceeds via carbocation intermediate b) Stereochem is retained c) Mechanism is bimolecular d) SN2 is more likely to occur at the tertiary position

c) mechanism is bimolecular

Purpose of using UV-Vis spec in this exp a) Provide concentration of product b) Confirm identity by matching lambda max to lit values c) Assess purity d) All

d) All

What data from the NMR can we use to distinguish between the two expected products a) Chemical shifts b) Peak shapes (multiplicity) c) Number of unique signals d) All of the above

d) All of the above

What is true regarding tandem reactions a) At least 2 subsequent reactions occur during the course of the tandem reaction b) Do not require purification between steps c) They are a process involving two or more bond-forming transformations which occur under the same reaction conditions d) All of the above

d) All of the above

Which of the following is not an advantage of using CO2 for extraction instead of pentane a) Non-flammable b) Less toxic c) Easily separated from the product d) Performed under high pressure

d) Performed under high pressure