Antiassociative Groupoids
  Given a groupoid $< G, \star >$, and $k \geq 3$, we say that $G$ is antiassociative iff for all $x_1, x_2, x_3 \in G$, $(x_1 \star x_2) \star x_3$ and $x_1 \star (x_2 \star x_3)$ are never equal. Generalizing this, $< G, \star >$ is $k$-antiassociative iff for all $x_1, x_2, ... x_k \in G$, any two distinct expressions made by putting parentheses in $x_1 \star x_2 \star x_3 \star ...x_k$ are never equal.   We prove that for every $k \geq 3$, there exist finite groupoids that are $k$-antiassociative. We then generalize this, investigating when other pairs of groupoid terms can be made never equal. 
Milton Braitt, David Hobby, Donald Silberger
math.RA