DIST(a=2.5,b=2,c=2.5) SHRINK
CH3Cl.xyz 0a 4c
HCOOH.xyz 1a 4b
HCOOH.xyz 1b 4c

# Trimolecular SN2
# a is O-Cl reacting pair
# b is the intra-acid hydrogen bond
# c is the H-Cl hydrogen bond