Nonpolar molecules tend to interact with other nonpolarmolecules. For example, molecules containing only hydrogenand carbon atoms—calledhydrocarbon molecules—are nonpolar.(Compare the electronegativities of hydrogen and carbon inTable 2.2 to see why.) In water these molecules tend to aggre-gate with one another rather than with the polar water mol-ecules. Therefore, nonpolar molecules are known ashydro-phobic(“water-hating”), and the interactions between themare calledhydrophobic interactions(FIGURE 2.6B). Hydrophobicsubstances do not really “hate” water—they can form weakinteractions with it, since the electronegativities of carbon andhydrogen are not exactly the same. But these interactions arefar weaker than the hydrogen bonds between the water mol-ecules, so the nonpolar substances tend to aggregate.Wateris polar.Polar molecules areattracted to water.Nonpolar molecules aremore attracted to oneanother than to water.(A)Hydrophilic(B)Hydrophobicδδδ+δ–δ–δ+The concepts of chemical bonding and electronegativ-ity (see Table 2.2) allow us to predict whether a mol-ecule will be polar or nonpolar, and how it will interactwith water. Typically, a difference in electronegativitygreater than 0.5 will result in polarity. For each of thebonds below, indicate:1. Whether the bond is polar or nonpolar2. If polar, which is thed+end3. How a molecule with the bond will interact withwater (hydrophilic or hydrophobic).N—HC—HC==OC—NO—HC—CH—HO—PAtoms interact and form moleculesAPPLY THE CONCEPTFIGURE 2.6Hydrophilic and Hydrophobic(A) Molecules withpolar covalent bonds are attracted to polar water (they are hydro-philic). (B) Molecules with nonpolar covalent bonds show greaterattraction to one another than to water (they are hydrophobic).The color convention in the models shown here (gray, H; red, O;black, C) is often used.