These names are usually formed according to some kind of system. Especially in chemistry "new" compounds are often named like that. Even a common word like alcohol gives rise to -ol compounds (like methanol) to indicate to a scientist that the two have certain chemical properties.
The compounds they name may or may not be in common use as nouns, and as such have lost their "name"-feeling.
If you want to capitalize arginine, you should, by rights, also capitalize alcohol, methanol and polypropylene. These are "names" given to substances, but they do not function like proper names.
In extremis, if you want to capitalize them, you should capitalize Water as well. It is, after all, the "proper name" given to dihydrogenoxide.
Of course, when a compound is given a trade mark name, it does get capitalized, even if the name seems to be systematically derived. However, if the name becomes very commonly used, it is possible that the trade mark name loses its "proper name" feel again, and we stop capitalizing it again.
Examples of that are Aspirin and Heroin (trademarks of Bayer), which are now written as aspirin and heroin.
Something similar happened with nylon and rayon (trademark of duPont) - their Teflon seems to be going the same way.
Apparently the rule found here is academic subjects are lower case unless they are the name of a language, culture, or religion.
He is taking math, literature, and English this semester.
Also you should capitalize if it is the formal name of a department at some institution, or on an official diploma or degree.
His work is in graph theory and data structures, but he has an Electrical Engineering degree.
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Best Answer
No, a spelling error. However, randomly capitalizing nouns to lend emphasis to them was common up to the 19th century. See for an example the original text of the Declaration of Independence, which begins "When in the Course of human events..."