Test Prep Test Prep Certifications OAT Questions & Answers

• Question 11:

  The reduction of an ester to an aldehyde can be done using which reagent?

  A. DIBALH

  B. Tri-t-butoxyaluminum hydride

  C. Lithium dialkylcuprate

  D. Phosphoylide (Wittig Reaction)

  E. Heat

  Correct Answer: A

  Addition of DIBALH (diisobutylaluminum hydride) indeed reduces an ester to an aldehyde. You should be familiar with all these reagents and know the effects they do to various reagents.

• Question 12:

  Name this compound:

  

  A. m-Bromotoluene

  B. o-Bromotoluene

  C. p-Bromotoluene

  D. p-Bromoxylene

  E. m-Bromocyclohexane

  Correct Answer: C

• Question 13:

  Which of the following are not part of Huckel's criteria for aromaticity?

  A. Be cyclic.

  B. Have one 2p orbital on each atom of the ring.

  C. Be planar.

  D. (4n+2) electrons

  E. All of the above are part of Huckel's criteria.

  Correct Answer: E

• Question 14:

  Which of the following has the highest melting point?

  A. Ethane

  B. 2,2-Dimethylpropane

  C. Propane

  D. Butane

  E. Pentane

  Correct Answer: B

  The general trend is the higher # of carbons, the higher the boiling point and melting point. There is a specific rule for this however that involves symmetry and branching. If the compound has branching and symmetry, then it has a higher melting point than its non-branched and symmetrical counterpart, which, in this example, 2,2-dimethylpropane (having 5 carbons) and pentane (also having 5 carbons, but lacking any branches).

• Question 15:

  

  A. Option A

  B. Option B

  C. Option C

  D. Option D

  E. Option E

  Correct Answer: A

  If an aldehyde is treated with ammonia (first step) along with a hydrogen and a metal catalyst, the end product is a primary amine.

• Question 16:

  

  

  A. Option A

  B. Option B

  C. Option C

  D. Option D

  E. Option E

  Correct Answer: C

• Question 17:

  What is the hybridization of this atom?

  

  A. sp

  B. sp2

  C. sp3

  D. s

  E. 2s2

  Correct Answer: B

  Pay special attention to the `+' symbol indicating a cation. If it lacked a positive or negative sign, it would be a sp3 hybridization.

• Question 18:

  Which of the following is an example of keto-enol tautomerism?

  

  A. Option A

  B. Option B

  C. Option C

  D. Option D

  E. Option E

  Correct Answer: E

  Keto-enol tautomerism is the equilibrium between a keto form and an enol form (alcohol) of a chemical. In this scenario, both answer choices B and C are applicable keto-enol tautomers, although the frequency of one form compared to another may be shifted.

• Question 19:

  Using the following infrared spectroscopy, determine the closest possible compound it may represent.

  

  A. Option A

  B. Option B

  C. Option C

  D. Option D

  E. Option E

  Correct Answer: D

  The peak at 1700 indicates the presence of a carbonyl group. The bands from 3000-2800 indicate C-H alkane stretches. Finally, the bands from 1300-1000 correlate with an ester group. This narrows down the answer to D: methyl propanoate.

• Question 20:

  Which of the following possesses the highest ionization energy?

  A. Lithium

  B. Carbon

  C. Nitrogen

  D. Sodium

  E. Fluorine

  Correct Answer: E

  Ionization energy increases as you go right and up in the periodic table. Fluorine is the right and uppermost choice.