Which group is shown as an ion hat are bonded to one of the

hat are bonded to one of the carbon atomsin a specific wayl role that organic compounds play in organisms. is important to analyze how these functional groups behave. TALE Six Functional Groups commonly Attached to Carbon Atoms Propertes Functional Group Acts as a base-tends to attract a proton to Carboxylic acids Acts as an acid-tends to lose a proton in solution Aldehydes, especially, react with certain oompounds produce larger molecules Highly polar, so makes compounds more soluble through hydrogen bonding with water; may also act as a weak acid and drop a proton Molecules with mora than one linked together store large amounts of chemical energy When present in proteins, can form disulfde Sulfhydry (S-S) bonds that contribute to protein structure HiN n these smuctura formulas, \"R stands for the rest of the molecule. EXERCISE Based on the olectronegativities of the atoms involved, predict whether each functional group is polar or nonpolar CHAPTER 2 Water and Carbon: The Chemical Basis of Life

Solution

Ans. a. Phosphate is an ion. An ion is a chemical species bearing a positive or negative charge. Note two negative charges on phosphate group.

Ans. b. The weak attractive interaction between a highly electronegative atom (F, O, N) and a H-atom covalently linked to any such highly electronegative atoms is called hydrogen bond. A larger difference in the electronegativity of the two atoms in a bond (say, O and H-atoms in a O- H bond) causes partial charge separation because the electronegative atom pulls the bond electrons slightly towards itself. Thus, the electronegative atom gets a partial negative charge and the less electronegative atom gets a partial positive charge. It makes the bond polar (two poles of charge- a partial negative pole of O-atom, and partial positive charge on H-atom). When a polar molecule comes in vicinity of another polar group or molecule, the partial positive charge on one group (molecule) is attracted by partial negative charge on another group (molecule) and vice versa. This weak attraction is what we call hydrogen bond.

A water (H₂O) molecule has both- I. a highly electronegative atom (O- atom), and II. a H-atom covalently linked to highly electronegative atom.

So, it can form H-bond with a molecule that has-

a highly electronegative atom >> form hydrogen bond with H-atom of water

a H-atom covalently linked to highly electronegative atom >> form hydrogen bond with O-atom of water

or both A and B

In the given set of groups, all groups (except- thiol, R-SH) have highly electronegative O-atom. Thus, they all form H-bonds with water.

The S-atoms in thiol group (R-SH) is weakly electronegative. So, the group has low polarity. The thiol group is also polar (polarity is weaker than that of alcohol) and can form H-bonds with water, too. However, the resultant H-bonds are much weaker than those formed due to alcohol (R-OH) groups.