Which of the functional groups below acts most like an acid in wa...

Question

Which of the functional groups below acts most like an acid in water?

Accepted Answer

Welcome back, everyone. Which of the following functional groups is responsible for giving acidic properties to organic compounds. Choice, a state carbon group, choice B state hydroxyl group, choice C states, alkyl group and choice D states, a carboxyl group. Let's recall our two definitions for acids and bases. We have our Bronte Lowry definition for an acid which is to act as a proton donor. And then our Bronte Lary definition for a base which is to act as a proton acceptor. Then we have our Lewis definition in which for an acid, a Lewis acid would be an electron pair accept her where a Lewis base we should recall would represent an electron pair donor. So based on these definitions and beginning with our first functional group listed carbonyl group, we're going to recall that a carbon is characterized by a carbon which has a pi bond or double bond to oxygen. Now, there are no available hydrogen ions or protons to be donated. Thus, our carbon or carbonyl is unable to act as a Bronzy Larry acid. And we can also note that for carbon to accept an electron pair would give it a negative charge. And thus, it cannot act as a Lewis acid. So let's rule out choice. A next we have a hydroxyl group. Recall that a hydroxyl group is characterized by a carbon chain bonded to oxygen which is bonded to hydrogen. So O h this proton in our hydroxyl group is stable and would only be able to be weakened by an electron withdrawing group such as a carbonyl. However, we don't have any electron withdrawing groups. And thus, this proton in hydroxyl does not have any acidic, the oxygen in our hydroxyl group is also stable and is bonded by its bonding preference of having two bonds and two known pairs on itself. And so it would not be likely to accept a proton or act as a bronzy larry base. So let's rule out choice B in choice C we have an L group recall that for an Alkie group, we would just be considering hydrocarbons which are chains of just carbons and hydrogens. So we can think of the molecule propane, which is a three carbon chain. However, notice that in propane, we do not have any acidic properties since carbon is not a very electron negative atom and nor is hydrogen. And thus, if any of our hydrogens in our structure of propane were to be donated, there would not be an electron negative atom that is capable of stabilizing that negative charge from the loss of a proton. And thus, an alkyl group cannot act as a bronzy larry acid. We can also note that there are no available opportunities for a hydrocarbon to accept a proton. And thus, it cannot act as a base. And also carbon being low in electron negativity means that if it were to accept an electron pair to act as a Lewis acid, it would be highly unstable. And so we can rule out choice c algal group and that leaves us with choice. D carboxyl group. Recall that for a carboxyl group, we have a carbonyl where carbon shares a pi bond to oxygen, that carbon is bonded to a R group. And then on the other side, we have a bond to a hydroxyl group due to the fact that our Carboni acts as an electron withdrawing group. Due to the fact that oxygen is more electron negative than hydrogen, the electrons in our carbon bond would be more strongly pulled or held by oxygen, creating a net negative inductive effect. And a partially negative charge on oxygen which weakens our electrons in our hydroxyl group or weakens our atoms in our hydroxyl group. So there's a weaker bond in our hydroxyl group, meaning that we have an acidic proton available to be donated. We can also perform resonance via the fact that we have our carbon group, which has a pi bond where the electrons can be redistributed to form resonance structures. And that would allow for the opportunity of an acetic proton to be donated in our car in our car carboxyl group. Again, due to that acidic proton from the weekend hydroxyl group. So choice D carboxyl group would be our final answer. As a functional group responsible for giving acidic properties to organic compounds. I hope this made sense and let us know if you have any questions.

Struggling with General Chemistry?

Which of the functional groups below acts most like an acid in water?

Watch next

Functional Groups in Chemistry practice set