A striking dependence on carbon number of the intercalation and interlayer amidation properties of alpha,omega-alkyldiamines H2N(CH2)nNH2 (n = 2-10) has been found for layered zirconium (carboxyethyl)phosphonate. Each alkyldiamine forms one or two intercalated phases in which the diamine molecules are arranged as a monolayer with their two ammonium termini binding to the carboxyl groups of any two adjacent phosphonate layers. The interlayer spacing vs n plots for the intercalated solids indicate that the axes of molecules in the monolayer are tilted by 19 or 59-degrees relative to the inorganic layer to form two groups of intercalates. Diamine with n less-than-or-equal-to 7 show a tendency to produce the high and low chain-tilt forms depending on the even and odd numbers of carbon atoms, respectively, but both forms coexist for n = 4, 6, and 7. For diamines with longer chain lengths, on the other hand, only the high chain-tilt form is observed. Upon heating at 120-degrees-C or above, all the diammonium-exchanged solids are condensed into their amide-functionalized forms, accompanying a partial desorption of the amine guests. The amidated phases are grouped into high and low chain-tilt forms depending only on the carbon chain length. The amidation also leads to an interlayer contraction of ca. 1.5 angstrom for the high chain-tilt form, but a slight interlayer expansion occurs for the other form. With an increase of the carbon number n, the temperature for the amidation to begin increases regularly up-and-down depending on the even or odd character of n.