Following is a structural formula for Erythromycin A, a...

Following is a structural formula for Erythromycin A, a macrolactone (macrolide) antibiotic. (a) How many hydroxyl groups are present? Classify each as primary $\left(1^{\circ}\right),$ secondary $\left(2^{\circ}\right),$ or tertiary $\left(3^{\circ}\right)$ (Chapter $10)$ (b) How many amine groups are present? Classify each as primary $\left(1^{\circ}\right),$ secondary $\left(2^{\circ}\right),$ or tertiary $\left(3^{\circ}\right)$ (Chapter $10)$ (c) Locate the ester group within the large 15 -member ring. (d) Four of the hydroxyl groups within Erythromycin A are involved in intramolecular (internal) hydrogen bonds. One of these is pointed out on the structural formula. Note that this hydrogen bond creates a five-membered ring. Locate the other three intramolecular hydrogen bonds and specify the size of the ring created by each. (Chapter $5)$

Following is a structural formula for Erythromycin
A, a macrolactone (macrolide) antibiotic.
(a) How many hydroxyl groups are present? Classify each as primary $\left(1^{\circ}\right),$ secondary $\left(2^{\circ}\right),$ or tertiary $\left(3^{\circ}\right)$ (Chapter $10)$
(b) How many amine groups are present? Classify each as primary $\left(1^{\circ}\right),$ secondary $\left(2^{\circ}\right),$ or tertiary $\left(3^{\circ}\right)$ (Chapter $10)$
(c) Locate the ester group within the large 15 -member ring.
(d) Four of the hydroxyl groups within Erythromycin A are involved in intramolecular (internal) hydrogen bonds. One of these is pointed out on the structural formula. Note that this hydrogen bond creates a five-membered ring. Locate the other three intramolecular hydrogen bonds and specify the size of the ring created by each. (Chapter $5)$

Key Concepts

Hydrogen Bond Induced Ring Formation

When intramolecular hydrogen bonding occurs, it can lead to the formation of bonded rings of varying sizes. The size of these rings, such as five-membered rings, affects the stability and conformation of the molecule. Recognizing how hydrogen bonds contribute to ring closure is important in areas like stereochemistry and conformational analysis in organic chemistry.

Intramolecular Hydrogen Bonding

This concept refers to hydrogen bonds that occur between functional groups within the same molecule, rather than between separate molecules. Such bonding can stabilize particular conformations by forming cyclic structures, which may influence the compound’s reactivity, solubility, and overall three?dimensional structure. Intramolecular hydrogen bonding is key in understanding molecular stability and behavior in complex organic systems.

Ester Functional Groups and Macrolactones

Ester groups are characterized by the -COO- linkage and are commonly formed through the condensation of a carboxylic acid and an alcohol. In the special case of macrolactones, the ester linkage is part of a large ring structure (macrocycle), which significantly influences the molecule’s stability, bioactivity, and conformational properties. Recognizing ester groups is crucial for understanding the chemical framework of lactone antibiotics and similar compounds.

Alcohol Classification (Primary, Secondary, Tertiary)

In organic chemistry, hydroxyl groups (-OH) can be connected to carbon atoms of varying substitution. A primary alcohol has the -OH attached to a carbon bonded to one other carbon, a secondary alcohol is attached to a carbon bonded to two other carbons, and a tertiary alcohol is attached to a carbon bonded to three other carbons. This classification affects the molecule's reactivity and the types of secondary reactions it may undergo.

Functional Group Analysis

This concept involves identifying the different functional groups within complex organic molecules. It requires recognizing distinct molecular fragments such as hydroxyl, amine, and ester groups, as these determine the compound’s reactivity, classification, and physical properties. Understanding how to parse and categorize these groups is essential in organic chemistry.

Amine Classification (Primary, Secondary, Tertiary)

Amines, which contain nitrogen atoms bonded to alkyl or aryl groups, are classified based on the number of carbon-containing groups attached to the nitrogen. A primary amine has one alkyl/aryl group and two hydrogen atoms, a secondary amine has two alkyl/aryl groups and one hydrogen, and a tertiary amine has three alkyl/aryl groups. This classification is useful in predicting the chemical behavior of amine groups in various reactions.

Transcript

00:01 Okay, so for this problem, we are looking at an antibiotic known as erythromycin, and this is the chemical structure that we are given for this antibiotic.

00:10 So now we are asked to identify a few different things about some of the groups present and some of the potential bonding.

00:17 So first we need to identify how many hydroxyl groups are present.

00:22 So first, let's just do a quick review on what a hydroxyl group is.

00:25 This is going to be a carbon bonded to an oh, so a carbon bonded to an alcohol.

00:31 And there are three different kinds of hydroxyl groups we need to be concerned with.

00:36 First is a primary hydroxyl group where this carbon that's bonded to the oh is only bonded to one other carbon.

00:47 That is primary.

00:49 Then we need to be concerned with a carbon that is bonded to two other carbons, which is secondary.

00:56 And then a carbon that is bonded to three other carbons, which we would call a tertiary.

01:00 Carbon.

01:01 So again, first degree is primary, second degree, that would be two carbons, and then third is tertiary where the carbon is bonded to three carbons.

01:14 Now keep in mind it's not the oxygen, it's the carbon that we need to be concerned with, the number of bonding that we will see.

01:24 Okay, so first let's identify how many hydroxyl groups we can locate on this molecule.

01:29 So we're looking for an oh -h bonded to a carbon.

01:31 So let's circle.

01:32 The carbons that are bonded to an lh.

01:35 This one right here is bonded to an oxygen and a hydrogen.

01:40 We see here.

01:44 We see here right next door.

01:47 Same thing.

01:49 Across the aisle, we see one right here.

01:54 And on the next street over, we see one here.

01:58 So how many do you see? let's look for the circled carbon molecules or atoms.

02:03 I see five.

02:04 So let's classify these now as being first degree, second degree, or third degree.

02:10 So if we quickly look, we will only see carbons that are in rings.

02:15 So they are going to be in these cyclical structures.

02:17 So they must be bonded to a minimum of two other atoms that aren't hydrogen.

02:27 So it can be carbon, oxygen, doesn't really matter.

02:30 As long as it's bonded to something besides hydrogen, then we need to classify it as such.

02:36 So there's no first degree, there's no primary hydroxyl groups, because that would have to be like this.

02:46 So if it's in a ring structure, we already see there's two here.

02:50 So that's impossible.

02:52 So we're just going to have second degree and third degree potentially.

02:55 So let's count starting at the bottom.

02:59 This carbon here, we see it's bonded to one, two, second degree.

03:06 This carbon here is bonded to one, two, two.

03:11 Three.

03:12 So that is going to be a third degree.

03:18 So i'll keep that tally there.

03:20 This carbon here is bonded to one, two.

03:24 That's another second degree.

03:26 This carbon is bonded to one, two, three.

03:30 It's a third degree.

03:31 And then this carbon is bonded to one, two.

03:34 So we have three second degree, or three secondary, and two tertiary hydroxyl groups present.

03:45 Beautiful.

03:46 So now we need to locate the ester group.

03:49 And let's just draw what an ester group looks like...

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