[crays]

Hi, i have another question i would like to ask. As my book said, an alpha D-glucose + a beta D-fructose will produce fructose. I understand how a 1,4-glycosidic linkage is is formed in a maltose but i don't know how a 1/2 glcosidic linkage is formed in sucrose. How do you count the carbons in a fructose molecule? I know in glucose its from the right to the left side. But not so how do you count the carbon from a fructose.. My teacher did not teach us how to... Any help is appreciated ~

[cliverlong]

Wikipedia is your friend

http://en.wikipedia.org/wiki/Disaccharide

for the structure of glucose (my search in Google was "sucrose linkage wiki")

Then clicking on "monosaccharide" in the wiki entry gives the start on naming

and clicking on "fructose" gives info on, surprisingly, fructose with lots of lovely structural formulae.

Now, what was the question? 

[crays]

Thanks for the reply. I've been to that site. But it doesn't tell me how do i count fructose by its carbon. Like i know glucose i count from the right side to the left, but where is fructose's first carbon atom ?

[cliverlong]

Thanks for the reply. I've been to that site. But it doesn't tell me how do i count fructose by its carbon. Like i know glucose i count from the right side to the left, but where is fructose's first carbon atom ?

I'm with you now

A bit of googling (it wasn't trivial to find,  I admit)

Turned up this link

http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/biochemistry/biochemi.htm

And searching for the term "Monosaccharides" in there gives an example of numbering - but I don't think the method is really spelled out.

Does that help?

Clive

[cliverlong]

I think answer may be hidden somewhere in here

http://www.blackwell-synergy.com/doi/pdf/10.1111/j.1432-1033.1971.tb01492.x

It's rather heavy going 

I didn't read all of it but page 2 has something on carbon numbering (locant carbon seems to be the term)

[cliverlong]

I will stop posting after this

The wikip entry

http://en.wikipedia.org/wiki/Haworth_projection

Shows a numbered glucose ring - but no explanation. I don't have an answer except it seems to be something to do with the position of the carbonyl group when (if) the monosaccharide can form a straight chain version. That may well be wrong. What a tortuous subject !

[crays]

Sorry if i pissed you off or something cliverlong, but with your advice, i've done some searching but still can't find anything useful. Until the wiki page you posted. I'm wondering how do you count the carbon atom as shown in
http://en.wikipedia.org/wiki/Haworth_projection for a fructose?

[cliverlong]

I'm wondering how do you count the carbon atom as shown in
http://en.wikipedia.org/wiki/Haworth_projection for a fructose?

Looking at the structural diagram on that page, isn't the "carbon numbering" on the diagram molecule what you want?

As to why it is numbered like that, all I can offer is the link to that old, and rather difficult to read, IUPAC document and on page 2 it suggests to me one starts numbering from the carbonyl when the molecule is in straight chain form. Of course, if there isn't a straight chain form of the molecule then that method won't work.

I'll make it clear this info is purely from Googling and reading. I'm not an expert on this - anyone else have a better, clearer reference than what I have provided?

Clive

Edit

Is this relevant?

http://www.chem.qmul.ac.uk/iupac/misc/psac.html

1.3. Atomic Numbering

The atom numbering of two monosaccharide units (a hexopyranose and a hexofuranose) is shown in Fig. 1. The notation used here conforms with that being proposed for specifying polynucleotide conformation. Atoms are thus designated C3, O2, H4, etc. The hydrogen atoms of a methylene group may be distinguished by an additional number, e.g. H61 and H62 where the lower number is selected for the pro-S atom [7]. When it is necessary to indicate the particular saccharide unit its number may be added in parenthesis, e.g. O3(i ), C4(i+1), H61(i-1).

(note to self. when in hole, stop digging)

[crays]

Thanks.

[Yggdrasil]

It is easiest to consider the numbering of the straight-chain forms of the monosaccharides.  Basically, the carbon chains are numbered to give the anomeric carbon the lowest number possible (the anomeric carbon is the carbon with two bonds to oxygen, e.g. the aldehyde [CHO group] in the straight chain form of glucose).  Since the anomeric carbon is at the end of glucose, it is assigned the number one and the other carbons are named accordingly.  In fructose, the anomeric carbon is not on the end.  So, the end closest to the anomeric carbon (the top carbon in the attached figure) is assigned the number 1, the anomeric carbon is assigned the number 2, and so on.

Figuring out the numbering in the cyclical forms of the sugars is more difficult and requires thinking about how the cyclization occurs (e.g. animated here: http://en.wikipedia.org/wiki/Image:Glucose_Fisher_to_Haworth.gif ).  Note that the anomeric carbon remains the same between the linear and cyclic form (for example, in both the linear and cyclic forms of fructose, carbon 2 always has two bonds to oxygen.  In the linear form, it is a double bond [a ketone] whereas in the cyclic form, it is in two single bonds [a ketal]).

[crays]

Thanks Yggdrasil, that is exactly what i am looking for haha. I've found out why already for now, the fructose is flipped (from the image you provided). So it forms a 1,2 glycosidic linkage. Thanks alot Yggdrasil. I can finally sleep now xD