One of the early answers was dimethyl phthalate.
Today, the word ""phthalate"" is usually associated with plastics and environmental debates. But nearly a century ago, compounds like dimethyl phthalate were also among the first synthetic insect repellents used to protect people from mosquitoes and other biting insects.
That history makes DMP unusually interesting.
It belongs to a family of chemicals that helped solve one of the plastics industry's earliest problems: how to make rigid materials softer and easier to process. Small molecules called plasticizers could slip between polymer chains and change how the material behaved—without changing the polymer itself.
Global Chemical Database