Figure 25.5 shows only the β-pyranose and β-furanose anomers of D-fructose. Draw the α-pyranose

Figure 25.5 shows only the β-pyranose and β-furanose anomers...

Key Concepts

Haworth Projection

This is a conventional method for representing the cyclic structure of sugars in a simplified two-dimensional form. It depicts the ring as a planar, almost triangular or circular shape with substituents either above or below the plane of the ring, which is crucial in understanding and drawing the structural differences between various anomers.

Pyranose and Furanose Forms

These terms refer to the different ring sizes that sugar molecules can form; pyranose forms are six-membered rings while furanose forms are five-membered. The ring size affects the overall geometry and the location of substituents, thereby impacting the chemical properties and biological functions of the sugar.

Cyclization of Carbohydrates

This concept explains the reaction in which a linear sugar molecule transforms into a cyclic form by an intramolecular reaction, typically forming a hemiacetal or hemiketal structure. This process involves the nucleophilic attack of a hydroxyl group on the carbonyl carbon, resulting in the formation of a ring structure that is fundamental to the structure and behavior of sugars.

Anomeric Carbon and Anomer Formation

The anomeric carbon is the carbon derived from the carbonyl group during cyclization, and its configuration (alpha or beta) is determined by the spatial orientation of the substituent at this center. The formation of ? and ? anomers is a key aspect of carbohydrate stereochemistry, influencing properties such as reactivity and interaction with other molecules.

Transcript

00:01 Okay, number 12, we are drawing the alpha pyranos and alpha -furinose version of d -fructose.

00:12 Okay, so what i have right here are pictures for the beta, beta -d -d -fructo -pyrinos and beta -d -fructo -purinose.

00:24 Okay, so i believe you have a similar, similar representation.

00:31 That is given in the book.

00:34 But anyways, the book, the point of this question is that the book doesn't give you the alpha, the alpha configuration.

00:43 So whenever we are differentiating between alpha and beta, the only carbon that we're looking at is this animic carbon right here.

00:54 So this, so this carbon right here for the pyranos and it's this carbon that we're looking at is this animeric carbon right here.

01:04 This enumeric carbon in the furinose.

01:08 Okay.

01:09 So this is the beta configuration.

01:12 So if you want to make it into alpha, all you need to do is switch the groups that are attached to that animeric carbon.

01:21 So we are switching these groups.

01:24 Okay.

01:25 So starting with the pyrrano's, pure nose version.

01:32 Okay, so i'll try my best to draw chair confirmation okay so it's not the easiest when you're dealing with it electronically but we're trying our best here then you have that equatorial alcohol okay so now that i have that let's switch those two groups right so on this beta configuration you have the alcohol group in the actual position so this time we're doing it equatorial.

02:24 So equatorial, and that's your alcohol group.

02:28 And then this time we're going to have the ch2 -o -h.

02:33 So this whole thing is the ch2o -h group in the actual position...

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