Lidocaine (xylocaine) is used as a local anesthetic and cardiac depressant.
a. Draw the condensed structural formula for the ammonium salt formed when lidocaine reacts with HCl.

Question

Lidocaine (xylocaine) is used as a local anesthetic and cardiac depressant.

Condensed structural formula of lidocaine, labeled as

a. Draw the condensed structural formula for the ammonium salt formed when lidocaine reacts with HCl.

Accepted Answer

Welcome back everyone. Procaine is a local anesthetic commonly used for inducing anesthesia, provide the structure of the ammonium salt produced when procaine reacts with hydrochloric acid. So we're given our structure and we want to understand that in this problem, we're going to observe an acid base reaction. Hydrochloric acid. HCL is an acid because essentially we have hydrogen bondage and electron chlorine atom, right. And therefore, in the gun structure, we're going to look for basic sites that can accept that hydrogen. And essentially we want to identify the atoms that can accept hydrogen most easily, right? So essentially those are hetero atoms with long pairs. Notice that we are given two oxygens. Let's recall that oxygens with T bonds, they will have two L pairs. And there are also t nitrogens, those nitrogens have three bonds, meaning they will have long pairs of electrons. So we once identified the most basic site in the given structure. And we once recall that the electronegativity of nitrogen is lower than the electron negativity of oxygen, which means that nitrogen will be more basic, generally, excluding all of the other factors that might be more complex. But let's not worry about them. In general, nitrogen atoms are more basic simply because they're less electron and they are willing to use their L pair more easily in bonding, right? Because essentially a lower electron negativity means that a long pair of electrons is held more loosely by an atom. So we can exclude oxygens because we have nitrogens present in the structure. And we want to understand which nitrogen is more basic. Is it nitrogen number one from anneline or is it *** number two? Now, let's first of all recall that nitrogens from amino groups are more basic whenever we have a higher degree of an amine. Now, what does that mean? Well, we can simply recall that primary A means are less basic than secondary A means and secondary A means are less basic than tertiary I means so basic, it increases with an increase in the alkyl groups because those alkyl groups are electron donors and they basically increase the electron density around nitrogen. So when we consider nht bonded to benzene, we can consider it a primary amine. And when we consider nitrogen, number two, it has three carbons around it. It's another amino group, right? And it's basically tertiary amine. So we can immediately state that this specific nitrogen is more basic. On the other hand, for more advanced students, we can also understand that any has its lump pair delocalized due to resonance with the adjacent benzene ring. So that lump pair is not even available for protonation, right? Or basically, it has a limited availability for protonation. So we can conclude that *** number two is much more basic than *** number one. And this is where the protein capture will take place. So what we're going to do is simply draw the nitrogen hydrogen bond because nitrogen has a long pair of electrons, right. So we're going to add the *** hygiene band. So we are essentially using the low pair of electrons to form that additional bond, which gives Ngen a formal positive charge. And since we're drawing the ammonium salt, we already have the nitrogen atom with four bonds, we simply want to include the counter ion which comes from HCL. And that would be chloride. It is not bonded to any of the atoms because it's actually the ionic bond, right? The ionic interaction. So we're just drawing it nearby and that will be the final structure of the salt itself. We can label it as the final answer. It is not procaine anymore. It's actually it's ammonium salt, right? So we don't need to worry about the original title for the modified structure. We can simply eliminate all of the other labels because there's they are not necessary for the final answer. So let's simply remove the analysis and that's it. We have our final structure for this problem. Thank you for watching.

Lidocaine (xylocaine) is used as a local anesthetic and cardiac depressant.

a. Draw the condensed structural formula for the ammonium salt formed when lidocaine reacts with HCl.

Verified video answer for a similar problem:

Key Concepts

Lidocaine Structure

Ammonium Salts

Condensed Structural Formula