chemical diagrammes

[lboogy]

Hi everyone,

 

I've had a look on the net before asking but couldn't really find anything. I'm looking for some sites that explain chemical diagrammes...I don't expect anyone to explain it just some good sites would be great. I'm not clear about the lines between the letters and also we some parts of the formula are drawn while other parts are written etc etc

 

Any links would be really appreciated!

[insane_alien]

what type of diagrams? there are vast amounts of different diagrams used in chemisty.

[Fred56]

What level of schooling were you looking at? Is this introductory Chemistry because there should be plenty of books available. Try a public library's Science section. Or have you tried looking for "molecular diagram", or what?

[lboogy]

Sorry, I should have been clearer. A Level biology (16-18 yrs), pre uni. I mean the biological molecules for things like gluscose for example. I have a couple of text books, but they just jump in and show one without explaining it....this was never part of the GCSE so it is a jump....

 

In particular, these are the things I don't understand:

a) does a line between 2 atoms mean it is chemically bonded? What signifies what type of bond it is? Are the covalent or ionic bonds?

b) When there is a line coming off the top right hand corner of the diagramme with a formula written down, is that the formula of the whole diagramme, or just the formula of another part of the molecule that isn't being drawn (I'm inclined to think the latter as the formula seems to actually be attached to the diagramme rather than as a title for the whole thing).

 

 

thanks guys!

[John Cuthber]

Well The answer to the first bit is easy.

" does a line between 2 atoms mean it is chemically bonded?"

Yes.

 

" What signifies what type of bond it is? Are the covalent or ionic bonds?"

Almost all the bonds in the molecules you see in biology are covalent. Sometimes there are hydrogen bonds indicated, but that's usually stated as such.

 

The second bit is more difficult because I'm afraid I don't know what you mean. Please could you post a link to an example.

[Fred56]

Often a diagram of something like a sugar or another large organic molecule is only partially represented. Which means that not all of the elements (especially hydrogen) are explicitly in the drawing, instead there's just a short line segment, usually on the "edges". This implies a hydrogen atom. Sometimes you see things like Cn which means a long aliphatic chain of carbons (with hydrogens attached). You need to understand what these and other "shortcuts" are.

[lboogy]

Hi John Cuthber & Fred56,

 

First of all thanks for your help. I think Fred56 has explained what I asked, but I'd really like to get a good understanding of these diagrammes...here is a link of what I mean:

 

http://www.ncbi.nlm.nih.gov/books/bv.fcgi?indexed=google&rid=mcb.figgrp.278

 

I guess what I'm trying to understand is say, when there is an O for oxygen. When a line goes off this O to another point in the hexagon which then has another line going to OH, does this mean that the O is covalently bonded to the other OH? Are all the atoms conected via lines covalently bonded? Also if the OH is also connected to another H there will that initial O be able to covalently bond with the OH as the OH will have all the outer shells full and therefore there wont be any need for that OH to chemically bond with other atoms?

 

Sorry in advance! I guess these are basic questions. I'd really like some website or book detailing them. I never came accross them at GCSe and all of a sudden they are present in A level, without no explanation!

 

sorry! i think they're known as structural formula's rather than chemical diagrammes.

[Fred56]

Hmm. A solid line implies covalent bonding. Hydrogen bonding is represented by a dotted line. This is probably the OH to H you are talking about. It's not complicated or anything, just a representation with some bits of the diagram omitted (implied).

[John Cuthber]

There's a really important thing to know about those diagrams (and yes, they are structural formulae). They don't bother to put all the carbon atoms in.

All the corners of the hexagons and pentagons, except there there is an "O" are carbon atoms. For example the glucose has 6 carbon atoms but only one is explicitly put there as a "C" in the diagram.

[lboogy]

John and Fred, once again thanks very much, I think I was just obscuring something that is simple!!!!