Primary sources are those where a researcher can find original data.
The major source of primary information are journals the majority of which are peer-reviewed.
Some chemical journals cover only specific areas while other cover a broad array of topics.
The two most important journals in this latter category are:
Angewandte Chemie - Internationl Edition (originally published in German)
In organic chemistry, major journal is:
Journal of Organic Chemistry - published by the American Chemical Society