Exam Questions

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Nitromethane (CH3NO2, pKa = 10) is more acidic than most organic acids.  Complete the acid-base reaction below with a valid Lewis dot structure (including formal charge and resonance structures if relevant) and explain why nitromethane is so much more acidic than ethane (pKa = 60).

Cyclobutane could adopt a flat conformation, but instead adopts a puckered conformation as shown below.  Indicate clearly the type of strain relieved in the puckered conformation and explain why this strain is not completely eliminated by the puckered conformation.

Which of the labeled N atoms will be basic and react readily with acids such as HCl?

 a. only B

b. only A

c. neither A or B

d. both A and B

e. cannot be determined

Predict the structure of the products of the following acid-base reaction and use curved arrows to indicate the direction of electron flow.  Indicate non-zero formal charge if applicable.

Monosubstituted cyclobutanes, such as methylcyclobutane, are similar to monosubstituted cyclohexanes in that there are two possible puckered conformations.  Provide both puckered conformations of methylcyclobutane, predict which is more stable, and clearly explain your rationale.

Methasterone (below) is a designer steroid with high liver toxicity that first surfaced in the mid-2000’s.  Provide a chair conformation of methasterone.

Indicate whether the circled protons homotopic, diastereotopic, enantiotopic, or none of these.

a. enantiotopic

b. homotopic

c.  diastereotopic

d. none of the above

 

Which C=O bond would have the largest dipole moment?

In the acid catalyzed hydrolysis of the methyl glycloside, which oxygen atom is protonated in the 1st step in the mechanism.

What is the respective multiplicity of the H’s labeled X and Y?  Do not be concerned with the possibility of diastereotopic protons.   

a. X= singlet, Y = singlet 

b. X= octet, Y = triplet 

c. X= nonet, Y = doublet 

d. X= septet, Y = doublet 

e. X= sextet, Y = singlet

 

 

 

 

 

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