The hydrogen bond basicity scale pK(HB) (logarithm of the formation co
nstant of 4-fluorophenol-base complexes in CCl4) has been measured for
nitro-compounds. This thermodynamic basicity scale is correlated to a
spectroscopic basicity scale. The Yukawa-Tsuno equation is obeyed in
the nitroaromatics. We have shown that nitroenamines are the most basi
c nitro-compounds presently known and have hydrogen bond basicity comp
arable to tributylamine.