94年國立台北科技大學有機高分子所(甲組)有機化學

Write the structures for the following compounds:

(1) Pyrrole (2) Thiophene(3) naphthalene (4) Phenylacetaldehyde(5) [15]-crown-5

Please answer the following questions for the pi molecular orbitals of1,3-butadiene:

(1) Draw the highest occupied molecular orbital for 1,3-butadiene.
(2) Draw the lowest unoccupied molecular orbital for 1,3-butadiene.
(3) Draw the highest energy molecular orbital for 1,3-butadiene

Compound X and Y are isomers with the molecular formula C10H12O. The IRspectrum of each compound shows a strong absorption band near 1710 cm^−1.The ¹H NMR spectrum of X shows a triplet at δ1.0 (3H), a quartet at δ2.5 (2H),singlet at δ3.6 (2H), and a multiplet between δ7.1 – 7.4 (5H). The ¹H NMRspectrum of Y shows a singlet at δ2.1 (3H), a triplet at δ2.7 (2H), a triplet atδ2.9 (2H), and a multiplet between δ7.1-7.3 (5H).

(1) The IR spectrum shows what functional group is present in these twoisomers?

(2) Propose structures for X and Y.

Write propagation steps for the monobromination of ethane in the presence oflight.

Which of the following conditions would you expect to be more reactive in anS_N1 reaction? Why?

(1) tert-Butyl bromide or n-butyl bromide.
(2) High concentration of the nucleophile or low concentration of thenucleophile.

Account for the following:

(1) The pKa of cyclopentadiene is 15, which is extraordinarily acidic for ahydrogen that is bonded to an sp3 hybridized carbon 

(2) In the gas phase the order of increasing basicity of amines is NH3 <CH₃NH₂ < (CH₃)₂NH < (CH₃)₃N.