Following are structural formulas for two local anesthetics...

Following are structural formulas for two local anesthetics used in dentistry. Lidocaine was introduced in 1948 and is now the most widely used local anesthetic for infiltration and regional anesthesia. Its hydrochloride salt is marketed under the name Xylocaine. Mepivacaine is faster-acting and somewhat longer lasting than lidocaine. Its hydrochloride salt is marketed under the name Carbocaine. (a) Name the functional groups in each anesthetic. (b) Which of these anesthetics are chiral? (c) Which nitrogen atom in each is the more basic? (d) What similarities in structure do you find between these compounds?

Following are structural formulas for two local anesthetics used in dentistry. Lidocaine was introduced in 1948 and is now the most widely used local anesthetic for infiltration and regional anesthesia. Its hydrochloride salt is marketed under the name Xylocaine. Mepivacaine is faster-acting and somewhat longer lasting than lidocaine. Its hydrochloride salt is marketed under the name Carbocaine.
(a) Name the functional groups in each anesthetic.
(b) Which of these anesthetics are chiral?
(c) Which nitrogen atom in each is the more basic?
(d) What similarities in structure do you find between these compounds?

Key Concepts

Functional Groups

This concept involves identifying specific atom groups within a molecule that determine its chemical behavior. For organic compounds like local anesthetics, key functional groups include aromatic rings, amide or ester linkages, and tertiary amines. Recognizing these groups is essential for understanding the compounds’ reactivity, solubility, and overall pharmacological profile.

Chirality

Chirality in chemistry refers to the existence of a molecule in two non-superimposable mirror-image forms, known as enantiomers. In pharmacology, identifying chiral centers is critical since different enantiomers can have distinct biological activities. The presence or absence of chirality in a drug molecule influences its synthesis, efficacy, and potential side effects.

Basicity in Nitrogen-containing Compounds

This concept focuses on understanding how the electronic environment around a nitrogen atom affects its ability to accept protons. In many organic compounds, especially those with amine groups, factors such as the degree of substitution, resonance effects, and proximity to electron-withdrawing or donating groups determine relative basicity. This has implications for how a drug interacts with its biological targets and its pharmacokinetic properties.

Structural Similarities in Local Anesthetics

This key concept involves identifying common structural features that define a class of compounds, such as local anesthetics. Typically, these compounds share an aromatic ring, an amide or ester linkage, and a tertiary amine. Recognizing these repeated patterns helps in understanding their mechanism of action, particularly their ability to block sodium channels in nerve cells.

Transcript

00:03 In this problem, we are shown three different anesthetics in first asked to identify the functional groups in each molecule.

00:12 So in lytocaine, we have a carbonyl group with an n next to it right here.

00:17 So that is an amid group.

00:22 And we also have an amine with three acule chains coming off of it.

00:27 So we have a tertiary amine.

00:34 In antitocaine, we also have an amine.

00:36 Group with that carbonyl with the end next to it.

00:44 And we also have an amine with, again, three alkyl chains coming off of it.

00:51 So that's another tertiary amine.

00:57 And in the epipivocaine, we also have that amid group right here.

01:10 And again, that amine with three alkyl groups.

01:15 So another tertiary amine.

01:19 The next part of the question asks us to identify which of these molecules are chiral.

01:26 So in order to do that, we have to identify if there are any chiral centers or stereocentors in these molecules.

01:33 So if we look at lytocaine, remember to be a chiral carbon, we need to have an sp3 carbon with four different groups attached to it.

01:43 So if we were to look at lydicane, the only s -3 carbons we have are these ones, this one, and the ones coming out the n.

01:53 These are ch3s, so the three of the same group, they're not chiral.

01:59 These also are ch3s, and these three carbons are ch2s, so they have two hydrogens and therefore are not chiral.

02:08 So there are no chiral centers in lidicane, so it is not chiral.

02:15 Atitocane, if we look at this one, we have, again, that same ch3s here.

02:23 The funnel ring and then also on the ends of these chains.

02:26 These are ch2s as well as this, ch3 and ch2.

02:32 But if we look at this one in the middle here, right here, this has an h, an n, a ch2, and a c that is a wanda to an o coming off it.

02:45 So this has a chiral center.

02:48 So this one is chiral.

02:51 And then lastly, if we look at the pivocaine, these two are ch3s as well as this one...

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