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 Chapter 2 - Distances Bond distance trends Limonene turns out to be a typical organic molecule as far as distances are concerned. In fact, nearly every organic molecule turns out to be typical. XY bond distances (and nonbond distances) seem to cluster in a narrow range for a wide variety of molecules. Therefore, we can use formulas to predict distances, and we can use distance data to construct formulas. Some typical bond distances are listed in the following table. As long as you remember that actual distances will vary a bit from the typical value, you can use these values to convert distance data into a molecular formula. Typical bond distances (in Å)
Of course, you do not need to memorize these values, but there are some interesting trends here that you should learn:
Although the second trend is fairly modest, chemists have used this trend to assign radii to different atoms, that is, chemists say atomic radius falls C > N > O >> H. Notice that this ordering seems related to the Periodic Table. Although I haven’t shown you any data to back up this next part, it turns out that atomic radius and position in the Periodic Table are correlated:
The two trends do not cover the same range of distances. The jump from F to Cl is quite large (0.7 to 0.95 Å) compared to the jump from F to O (0.7 to 0.73 Å). This is an important sign that, within a column, the chemistry of lower elements (Cl, Br, I) may be very different from the highest one (F).
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