Question

Using the values of electronegativity given in Table 1.5, predict which indicated bond in each set is more polar, and using the symbols \(\delta+\) and \(\delta-\), show the direction of its polarity. (a) \(\mathrm{CH}_{3}-\mathrm{OH}\) or \(\mathrm{CH}_{3} \mathrm{O}-\mathrm{H}\) (b) \(\mathrm{CH}_{3}-\mathrm{NH}_{2}\) or \(\mathrm{CH}_{3}-\mathrm{PH}_{2}\) (c) \(\mathrm{CH}_{3}-\mathrm{SH}\) or \(\mathrm{CH}_{3} \mathrm{~S}-\mathrm{H}\) (d) \(\mathrm{CH}_{3}-\mathrm{F}\) or \(\mathrm{H}-\mathrm{F}\)

Short answer

Answer: The more polar bonds are CH3O-H, CH3-NH2, CH3S-H, and H-F. The polarity directions are CH3O-δ+ to O-δ-, CH3-δ+ to N-δ-, CH3S-δ+ to H-δ-, and H-δ+ to F-δ-, respectively.

Step-by-step solution

Identify electronegativity values for each atom

In order to determine the polarity of the bonds, we first need to know the electronegativity values for each atom involved. Table 1.5 should provide these values for C, H, O, N, P, S, and F. Let's write these values down for future reference: - C: 2.5 - H: 2.1 - O: 3.5 - N: 3.0 - P: 2.1 - S: 2.5 - F: 4.0

Calculate the difference in electronegativity for each bond

Now, for each bond in each set, we will calculate the difference in electronegativities between the bonded atoms. The greater the difference, the more polar the bond. (a) CH3-OH vs CH3O-H - For CH3-OH, difference = |3.5 - 2.5| = 1.0 - For CH3O-H, difference = |3.5 - 2.1| = 1.4 (b) CH3-NH2 vs CH3-PH2 - For CH3-NH2, difference = |3.0 - 2.5| = 0.5 - For CH3-PH2, difference = |2.1 - 2.5| = 0.4 (c) CH3-SH vs CH3S-H - For CH3-SH, difference = |2.5 - 2.5| = 0 - For CH3S-H, difference = |2.5 - 2.1| = 0.4 (d) CH3-F vs H-F - For CH3-F, difference = |4.0 - 2.5| = 1.5 - For H-F, difference = |4.0 - 2.1| = 1.9

Determine the more polar bond and the direction of its polarity

Now that we have the differences in electronegativity for each bond, we can compare them within each set and determine the more polar bond, as well as the direction of their polarity. (a) CH3-OH or CH3O-H: - CH3O-H is more polar (difference of 1.4) - Polarity: CH3O-\(\delta+\) to O-\(\delta-\) (b) CH3-NH2 or CH3-PH2: - CH3-NH2 is more polar (difference of 0.5) - Polarity: CH3-\(\delta+\) to N-\(\delta-\) (c) CH3-SH or CH3S-H: - CH3S-H is more polar (difference of 0.4) - Polarity: CH3S-\(\delta+\) to H-\(\delta-\) (d) CH3-F or H-F: - H-F is more polar (difference of 1.9) - Polarity: H-\(\delta+\) to F-\(\delta-\) Therefore, the more polar bonds are CH3O-H, CH3-NH2, CH3S-H, and H-F, with the polarity directions as indicated above.