How to prevent autocorrection to change chemical formulas and unit notations

I use LibreOffice (formerly OpenOffice) for far more than 10 years with dutch language and regional settings on a linux platform. As a chemical technologist I have often to write chemical formula’s (i.e. NO2 or CaCO3) and units (MWh). In this type of ‘words’ the upper and lower cases of letters have a specific meaning and must not be changed.
Regularly I stumble against the auto-correction function of LO. It changes the formulas or units wrongly. There have been past versions of LO where I found how to switch off the auto-correction function, but in the current version I am not able to switch the correction off (cannot find where).
The number of chemical formulas and different unit notations is to large to build a list of exceptions.
How to proceed?

You didn’t mention your LO version nor your OS name.

There have been past versions of LO where I found how to switch off the auto-correction function

You understand that after such a statement, mention of your current version is important.

In addition, you tagged your question with the name of all components (except Base and Math), meaning you want a solution for every component. The answers below are valid for 7.4.3.2.

  • Writer: disable Tools>AutoCorrect>While Typing
  • Calc: open Tools>AutoCorrect Options, Options tab and untick Use replacement table (works also in all other components)
  • Impress: same as Calc
  • Draw: same as Calc

Thank you. It worked in my version 7.3.6.2 under OpenSuse 15.3.
I expected these switches in tools>options (where I think they belong) and not in ‘tools>autocorrect options’.