Diprotic Substance log ZpH Curve Shapes 12 Cases

As noted, lipophilicity equations for cases 2a-2c in Table 1 only represent one-species partitioning. If in addition to the neutral species, an ion pair also partitions, the basic Eq. (19) can be solved for the condition. Fig. 12 a-121 represent the 12 resulting cases.

The diprotic molecules we considered earlier, salicylic acid, morphine, and nicotine, are examples of cases (a), (b), and (c), respectively. We will later point out other examples.

LIPOPHILICITY PROFILE

fogO

LIPOPHILICITY PROFILE

logD

logD

LIPOPHILICITY PROFILE

Cos» Cd): pKa,-5. pK„a-S. logPCXHa)-2. logP(XH)-

LIPOPHILICITY PROFILE

LIPOPHILICITY PROFILE

Co» Co): pK„,-5. PK„a-B. ogP (X Hj) - Ice l-'0< H ) - 2 Co3. (0 pK.,-5. pK„a-B. 'oqP(XH,)= 1 'ogP(XH)-^

LIPOPHILICITY PROFILE

Cos» Cd): pKa,-5. pK„a-S. logPCXHa)-2. logP(XH)-

logD

LIPOPHILICITY PROFILE

Cos. <g): pK„,=5. pK0l-a. logPCXH)-2. IcgPfX)-;

logD

LIPOPHILICITY PROFILE

LIPOPHILICITY PROFILE

LIPOPHILICITY PROFILE

Cos. <g): pK„,=5. pK0l-a. logPCXH)-2. IcgPfX)-;

Cosa CM: PK„,-5. pK.a—S, !ogPCXH)-]agP(X)—2 Cose CO: pK.i —5. pK.a—8. ogP(XH)=1 togPCX)=2

logD

logD

LIPOPHILICITY PROFILE

Coso (j): pK„,-5. pK„-e. logPCXHa)...2, logPCX) =

LIPOPHILICITY PROFILE

LIPOPHILICITY PROFILE

logD

LIPOPHILICITY PROFILE

Coso (j): pK„,-5. pK„-e. logPCXHa)...2, logPCX) =

Cos« (k) pK.,-5, pK„a—B. logPCXHs)-logP(x)-2 Coso CO: pK0,-5. pK=i-6. logPCXHa) = 1. logP(X) = 2

logD

logD

Figure 12. Twelve possible shape types of lipophilicity plots for a diprotic molecule exhibiting two-species lipid partitioning.

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