Chem 1120 Quiz 4 Key

 

  1. The oxygen atom and all of the carbons except those in the ethyl and methyl groups are sp2 hybridized and have trigonal planar geometry. The ethyl and methyl carbons and the nitrogen atom are sp3 hybridized and have tetrahedral and pyramidal geometries respectively. All atoms in this are covalently bonded; the atoms involved in sp2 hybridization are involved in double bonds. This compound can participate in London forces (benzene ring, ethyl and methyl groups) and in dipole-dipole interactions (carbonyl atoms, nitrogen).
  2. The product is the result of a two step reaction that results in the formation of a hemi-acetal which is quickly converted to an acetal. Working backwards from the acetal, the starting material was 2-hexanone. Changes in hybridization and geometry occur to the carbonyl carbon and the carbonyl oxygen; both are converted from sp2 hybridization and trigonal planar geometry to sp3 hybridization and tetrahedral geometry.
    quiz 5b-2-answer
  3. These reactions are similar in that each results in the reduction of (i.e., addition of hydrogen to) the carbonyl oxygen. The fundamental difference between the two reactions lies in the way by which hydrogenation is accomplished. See your notes for more information.
    quiz 5b-3 answer
  4. The selective oxidation of 2-methylpropanal results in the formation of 2-methylpropanoic acid (C4H8O2), while the selective oxidation of 1-hydroxy-2-butanone (C4H8O2) results in the formation of 2-ketobutanoic acid.
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    The balanced reaction equation for the combustion of 2-methylpropanoic acid is C4H8O2 + 5 O2 -> 4 CO2 + 4 H2O and the amount of oxygen required for the combustion of 25.0 grams is (25.0 g C4H8O2) x (1 mol C4H8O2 / 88 g C4H8O2) x (5 mol O2 / 1 mol C4H8O2) x (32 g O2 / 1 mol O2) = 45.5 g O2 .

    The balanced equation for the combustion of 2-ketobutanoic acid is C4H6O3 + 4 O2 -> 4 CO2 + 3 H2O and the amount of oxygen required for the combustion of 25.0 grams is (25.0 g C4H6O3) x (1 mol C4H8O2 / 102 g C4H6O3) x (4 mol O2 / 1 mol C4H6O3) x (32 g O2 / 1 mol O2) = 31.4 g O2 .
  5. Note that the ester formed could also be called 2-methyl-2-propyl 2,4-dimethylpentanoate or 2-methylisopropyl 2,4-dimethylpentanoate. The alcohol used could also be called tert-butanol.