The FTIR spectra of all four phosphate molecules were recorded and the frequency for phosphoryl group vibration was observed to shift slightly upwards as the length of the substituent groups increased (Table ). This is consistent with results reported by Wagner, who related this trend to decreasing O-P bond order as the electronegativity of the ester group increases. The presence of more O atoms in the ester groups withdraws electrons away from the phosphorus atom, which compensates by increasing the bond order in the phosphoryl -bond. The downward shift of 5 cm -1 going from TBP to T i BP suggests that the branched butyl groups are slightly more electron donating than linear groups, leading to a small decrease in P=O bond order. The 31 P NMR spectra for all four phosphate molecules were also noted, and the chemical shifts tended to shift upfield as the length of the substituent groups increased (also Table ). This is also consistent with results reported by Gorenstein, who related this trend to increasing O-P-O bond angles in phosphate esters. Substituents with greater steric bulk force themselves further apart, leading to larger O-P-O bond angles, which more effectively shields the 31 P nucleus.