By considering the functional groups in a compound, we can make many predictions about a compound that we have never before encountered, and perhaps has never even been synthesized. Bond polarity is a function of the difference in electronegativity of the atoms that make up a bond. Plants died when exposed to one enantiomer of 2,4-DP but were immune to the other enantiomer. Other studies find no noticeable toxicity in birds, but significant toxicity to fish and aquatic invertebrates. Thus the melting points of the two enantiomers of 2,4-DP are equal.
Herbicidal action is a biological effect.
Such biological effects are often brought about by interaction with a biological structure such as an enzyme or receptor. These structures have distinct three-dimensional shapes because they are made of chiral building blocks such as amino acids. One enantiomer of 2,4-DP might fit well into an enzyme or receptor, whereas the enantiomer may not fit as well. If the enantiomers bind differently, they will cause different biological effects. If the right hand is an enantiomer of 2,4-DP it would active the right glove enzyme but not the left glove enzyme.