John E. McMurry
ISBN #9781285842912
3rd Edition
1,528 Questions
Homework Questions
This chapter establishes a foundation in describing molecular reactivity by exploring polar covalent bonds, the effects of differences in electronegativity, and the resulting dipole moments. The calculation of formal charges and the understanding of resonance are key to predicting structure and reactivity in organic molecules. Additionally, the chapter underscores the importance of acid–base concepts using both the Brønsted–Lowry and Lewis definitions, highlights the utility of pKa values in comparing acid and base strengths, and explains the significance of noncovalent interactions in determining the physical and biological properties of molecules.
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CONCEPT
DEFINITION
Definition: The study of molecular reactivity via polar covalent bonds where differences in electronegativity create dipole moments, guiding acid–base behavior.
The study of molecular reactivity via polar covalent bonds where differences in electronegativity create dipole moments, guiding acid–base behavior. •
Which element in each of the following pairs is more electronegative? (a) Li or H (b) B or Br (c) Cl or I (d) C or H
Use the $\delta+/ \delta-$ convention to show the direction of expected polarity for each of the bonds indicated. (a) $\mathrm{H}_{3} \mathrm{C}-\mathrm{Cl}$ (b) $\mathrm{H}_{3} \mathrm{C}-\mathrm{NH}_{2}$ (c) $\mathrm{H}_{2} \mathrm{~N}-\mathrm{H}$ (d) $\mathrm{H}_{3} \mathrm{C}-\mathrm{SH}$ (e) $\mathrm{H}_{3} \mathrm{C}-\mathrm{MgBr}$ (f) $\mathrm{H}_{3} \mathrm{C}-\mathrm{F}$
Use the electronegativity values shown in Figure 2.2 to rank the following bonds from least polar to most polar: $\mathrm{H}_{3} \mathrm{C}-\mathrm{Li}, \mathrm{H}_{3} \mathrm{C}-\mathrm{K}, \mathrm{H}_{3} \mathrm{C}-\mathrm{F}, \mathrm{H}_{3} \mathrm{C}-\mathrm{MgBr}$ $\mathrm{H}_{3} \mathrm{C}-\mathrm{OH}$
Look at the following electrostatic potential map of methylamine, a substance responsible for the odor of rotting fish, and tell the direction of polarization of the $\mathrm{C}-\mathrm{N}$ bond:
Ethylene glycol, HOCH $_{2} \mathrm{CH}_{2} \mathrm{OH}$, has zero dipole moment even though carbonoxygen bonds are strongly polar and oxygen has two lone pairs of electrons. Explain.