  Let $A$ be a semiprime 2 and 3-torsion free non-commutative associative
algebra. We show that the Lie algebra $\der(A)$ of (associative) derivations of
$A$ is strongly non-degenerate, which is a strong form of semiprimeness for Lie
algebras, under some additional restrictions on the center of $A$. This result
follows from a description of the quadratic annihilator of a general Lie
algebra inside appropriate Lie overalgebras. Similar results are obtained for
an associative algebra $A$ with involution and the Lie algebra $\sder(A)$ of
involution preserving derivations of $A$.
