Three classes of chemicals are monitored under this Convention, with sulfur and nitrogen mustard grouped in Schedule 1, as substances with no use other than in chemical warfare.
From the en.wikipedia.org
The top molecule is bound reversibly, but the lower one is bound covalently as it has reacted with an amino acid residue through its nitrogen mustard group.
From the en.wikipedia.org
Grow a speedy green crop such as mustard or lupins in beds which have been previously used for low-nitrogen crops such as parsnip, onions or carrots.