PHOSPHORAMIDATE COMPOUNDS COMPRISE A DIVERSE CLASS OF CHEMICALS DUE TO THEIR POTENTIAL APPLICATIONS AS ACETYL CHOLINESTERASE AND UREASE INHIBITORS, ANTIOXIDANTS, AND ANTIRUST ADDITIVES IN LUBRICATING OILS, PESTICIDES, AND ANTICANCER DRUGS [1,2]. THE STUDY ON DERIVATIVES OF THIS CLASS WITH FORMULA (R1O)P(O)(NHR2)2 IS IMPORTANT OWING TO THEIR CRUCIAL ROLE IN VARIOUS AREAS OF SCIENCE INCLUDING SYNTHESIS, COORDINATION, BIOMEDICINE, AND THEORETICAL MATTERS [3, 4]. HENCE, IN THIS WORK, THREE NEW DERIVATIVES WERE PREPARED BY THE REACTION OF PHENY DICHLORO PHOSPHATE WITH THE CYCLIC AMINES (THREE, FIVE AND SIX RINGS) IN THE PRESENCE OF TRIETHYLAMINE AS HCL SCAVENGER IN DRY CHLOROFORM AT 0ºC. AFTER STIRRING FOR 24 H, THE WHITE PRECIPITATES WERE FILTERED AND THE PRODUCTS WERE WASHED WITH COOL WATER. THE PRODUCTS WERE CHARACTERIZED BY 13C, 31P, 1H NMR AND IR. THE PURPOSE OF THE PRESENT STUDY WAS TO INVESTIGATE THE EFFECT OF RING SIZE ON STRUCTURAL AND BIOLOGICAL PROPERTIES. SINCE, MOLECULES WERE SCREENED FOR IN VITRO ANTIMICROBIAL ACTIVITIES AGAINST TWO GRAM NEGATIVE BACTERIA (E. COLI AND P. AERUGINOSA) AND THREE GRAM POSITIVE BACTERIA (B. SUBTILIS, S. AUREUS, AND B. CEREUS). BESIDES, WE OPTIMIZED THE STRUCTURES OF THE TITLED MOLECULES BY DFT AND NBO CALCULATIONS TO OBTAIN THE TITLED PROPERTIES AND AIM ANALYSES TO INVESTIGATE OF THE ELECTRONIC ASPECTS OF HYDROGEN BONDS.