HYDROGEN BONDING 



71 







\2.83 / 



\ /3.02 P 



\ / /2.82 



0.2.94 \ / / 



H 



0'-- 



2.97^ - - -^/° 



/ 



nh' 



X 



/ 



/ 



/ 



H 



/^ 



/ 



NH 



/ 



/ 



H- 



3.07 



1.73 



L47 



0-_ 

 \ 



\ 

 \ 



HN 



\ 



\ 



HN 



HN 



Fig. 9. One sulfamic acid molecule and its twelve closest neighbors in the crystal, 

 showing the hydrogen bond system suggested by Kanda and King. Note the presence 

 of two bifurcated hydrogen bonds. 



Fig. 10. Stereographic projection down the S — N bond in sulfamic acid. The num- 

 ber prefixes for each atom give which of the eight equivalent molecules in the unit cell 

 that atom belongs to. The numbering of Kanda and King has been retained. The dot- 

 ted lines and open circles give the orientation of the — SO3 part of the molecule, the 

 solid lines and filled circles give the best orientation for the — NH3 part of the mole- 

 cule. Note that when the — NH3 group is rotated to bring two of the hydrogen atoms 

 as close as possible to oxygen atoms, the third hydrogen atom (upper left) is in a posi- 

 tion unfavorable for hydrogen bond formation. 



