Indexing of salts
Thanks for your question.
In cases like this I'd definitely go down the structure search route since structure searches are precise and comprehensive - provided you enter the right query.
So from the Landing Page, I'd click Create Structure or Reaction Drawing, then in Create structure template from name enter say: 2-hydroxypyridine. I'd search this structure As drawn and I'd definitely include Tautomers. I'd consider the defaults but at this stage I'd probably leave them as they are.
After you Transfer and Search you find each substance has its own Substance Record. I'd browse some of the other answers just for interest, but there are not many documents for them.
The question now is: Which tautomer is indexed? The answer is that it depends on what was in the original document. If 2-hydroxypyridine was the focus then that would be the indexed substance; similarly if 2-pyridone was the focus - it would be the indexed substance. If the original document discussed both, then while I am not certain of the indexing policy, I think both would be indexed.
I hope this helps.
Damon
People have asked about the indexing of salts in different databases.
There are two parts of the problem:
- there are different "classes" of salts;
- databases may (or may not) have different indexing policies for the different classes.
We can have salts of simple alkali/alkaline earth metals with non carbon-containing or carbon-containing acids, or of simple halides with non carbon-containing or carbon containing bases, or salts of carbon-containing acids with carbon-containing bases. We also talk about hard and soft acids and bases, but the chemical difference here usually relates to the extent of ionisation of the "bond" between the different atoms. Then, when is something a salt or a coordination compound? Calcium hydroxide is normally considered a salt, so is calcium acetate - but is calcium oxalate a salt or a coordination compound? Then, what happens with "hydrates" - are they hydrates, salts or coordination compounds? (Incidentally, I once made a lithium salt of a phosphinic acid, and it gave a strong molecular ion in the mass spectrum - possible only because of a very "covalent" Li - O bond.)
Given all that, the representation of substances in computer databases needs to have clear cut rules and the different databases may have different policies. Hence, in different databases, lithium acetylide may have a different representation from lithium acetate. Further, take ferrocene. When it was first made chemists thought of different ways to represent its structure. These structures were published in papers and databases entered the structures accodingly. However, years later it was realised the actual structure was quite different - that being the case should all the previous structures be deleted, or changed? Are databases always going to make "retrospective corrections"?
The issue here is not necessarily with computers, or the policies of people who create databases, but perhaps more with the (fascinating) complexities of chemical substances.
Damon