We next analyzed F28oCNF, where crystallography showed that the C≡N group is solvent exposed and Hbonded to bulk water; MD indicated this interaction has an average HB distance and angle of 3.00 Å and 163° (Fig. ). Using eq. 7, we obtained 〈∆𝜈̅ 𝐻𝐵, (𝑑, 𝜃)〉 = 25.4 cm -1 (Fig. ). However, unlike F92oCNF, we noted a considerable discrepancy between this value and ∆𝜈̅ 𝐻𝐵,𝑜𝑏𝑠 when we analyzed F28oCNF's IR spectra (Fig. ). F28oCNF has an average electric field of -64.9 MV/cm in the MD H-bonding fraction (see ref. ), and the pure VSE effect predicts the C≡N's peak position to be at 2219.1 cm -1 (see values in Fig. and red line in Fig. ). However, in the experimental IR spectrum, we observe a peak position at 2230.9 cm -1 , which leads to ∆𝜈̅ 𝐻𝐵,𝑜𝑏𝑠 = 11.8 cm -1 , only half as large as 〈∆𝜈̅ 𝐻𝐵, (𝑑, 𝜃)〉 (this is visually demonstrated in Fig. by the red line appearing halfway along the dashed double headed arrow). We hypothesized that this discrepancy may be related to F28oCNF's H-bonding with the highly fluctuating solvent environment, in which the C≡N rapidly alternates between H-bonding and non-H-bonding states (SI Section 8).