Ring vibrations etc

Ring vibrations etc. Short and Thompson [18] have drawn attention to the fact that a series of chloro-substituted and ethoxy-substituted pyrimidines which they have examined all absorb near 990 cm and near 810 cm . The former was assigned to a ring vibration, and the latter thought to be due to this also, although the 

The 810 cm band is now known to be a hydrogen deformation and its position is therefore more sensitive to the position of substituents. In 2-substituted pyrimidines it is between 818 and 799 cm but values up to 860 cm can be reached with more complex substitution. 

---