Hill Order is a system of writing chemical formulae. If the compound for which the formula is being written contains carbon, the number of carbon atoms is listed first. The number of hydrogen atoms is listed next. Every other element is listed subsequently in alphabetical order.
If the compound for which the formula is being written does not contain carbon, every element (including hydrogen) is listed in alphabetical order.
A list of chemical formulas (e.g. in an index) is compiled alphabetically according to the first element in each formula.
An example of a list:
You can also search compounds by their Reaxys Registry Numbers (also referred to as RX-RNs). But unlike CAS numbers, these numbers do not refer to biomolecules like enzymes or commercial mixtures. These numbers can be used in both Reaxys and Scifinder.
A registry number (sometimes seen as RN) is a unique identifying number assigned to a chemical compound, commercial mixture, or an entire class of molecules (e.g. categories of enzymes). A CAS registry number is one assigned by the Chemical Abstracts Service (CAS) once a substance is registered with them. CAS registry numbers are assigned to structures rather than names, and look something like this: 15687-27-1 or 71-43-2.
Note: isomers that have the same molecular formula will each have their own CAS numbers.
Most online databases will allow you to type a CAS registry number into the search bar and it will find your desired results. Some will also have the option to select CAS registry number from a drop down menu of search fields, which may improve the specificity of the search.
Some databases that support searching with CAS registry number:
DOI stands for digital object identifier. A DOI looks something like this: 10.1021/ja100167z. They are typically found as part of the citation information for journal articles published in the sciences. DOIs may also be used for electronic books or book chapters. A DOI uniquely identifies a publication – no two publications will have the same DOI, and one publication in multiple databases will always have the same DOI. When you search using a DOI, that particular article will always be the result. This is helpful because it saves you from having to remember the journal title, article title, volume numbers and so forth!
A DOI can be found anywhere in a journal article – under the author information or the article title, or at the top or bottom of the first page. DOIs can also be found in database search results, or by clicking on the detailed record for the article you are interested in.
Some articles may not have a DOI. For example, articles published outside of the sciences tend not to have DOIs. An article may also not have a DOI if it was published before DOIs existed (though some older articles will have had DOIs added!). DOIs are becoming more common in the scientific community, so recently published articles tend to have a DOI assigned to them.
DOIs can be used to locate an article in particular databases like SciFinder, Reaxys, Web of Science and SCOPUS. DOIs can also be searched through Google.
Find the full text of an article using the DOI
The purpose of a DOI is to give a distinct alpha-numeric name to an article to allow that article to be uniquely identified without using potentially ambiguous search methods such as journal titles or abbreviations, names of authors, or article titles.
Because of this, you can use a DOI to check if UofT has electronic access to the full text for a specific article by using the Article Finder. Article Finder can be accessed through the UTL homepage – it is located below the catalogue search bar on the right. On the Article Finder screen, there is an option to search specifically by a DOI. Plug the DOI into the box and click search – you do not need to provide any information other than the DOI! This brings up a page that allows you to select the provider you wish to access the full text through.
Create a permanent link using a DOI
DOIs can also be used to create a permanent link to the article. This is helpful if you want to share the article with someone, or can be used as an easy way to bring up an article in the future. Building a permanent link using a DOI can be done through either of the following methods:
Using Article Finder:
This link will take you the page that displays the providers for your article.
Building your own link:
This link will take you directly to your article - you will not have a choice of providers (if you are off campus it will ask for your UTORid and password first).
An InChI is a string of characters used to uniquely identify chemical substances. This system was developed by IUPAC to make searching for molecular information online easier. The InChI has been further condensed into a shorter string called an InChIKey. The InChIKey remains a unique identifier, and can be searched in some database. An InChiKey can also be plugged into internet search engines such as Google to retrieve information about a particular substance from internet sources. An InChIKey will look something like this: WPYMKLBDIGXBTP-UHFFFAOYAD
Notice the difference between an InChI and an InChIKey:
Image from ChemSpider
Further Information:
