Strong Covalent Hydration of Terephthalaldehyde

Abstract

Spectrophotometric and electroanalytical studies indicate that one of the formyl groups of terephthalaldehyde in aqueous solution is present in about 23% as a geminal diol. Stronger covalent hydration of CHO in terephthalaldehyde than in p-nitrobenzaldehyde is attributed to a strong resonance interaction between the two formyl groups.

Control of the Ketone to gem-Diol Equilibrium by Host−Guest Interactions

“…The relative ratio of the two forms, and therefore the value of each ketone ⇌ gem -diol equilibrium constant ( K diol ), is extracted directly from the 1 H NMR spectra. K diol data show a good Hammett correlation (Figure ) with a reaction constant ρ = 1.31 ± 0.02, which is similar to values reported for substituted benzaldehydes (1.71−1.75) 4 Substitution effect for the keto/ gem -diol equilibrium in D 2 O/0.1 M KCl with and without 1.0 molar equiv of CB[7] .…”

Comparison of Solution Chemistries of Orthophthalaldehyde and 2,3-Naphthalenedicarboxaldehyde

“…The large size of the difference indicates that it is possible to exclude the role of an intramolecular hydrogen bonding in aqueous solutions, where intermolecular hydrogen bonding predominates. The strong resonance interaction between the two formyl groups in OPA resembles that which has recently been reported for the two formyl groups in terephthalaldehyde. Such interaction results also in the stronger hydration of OPA than NDA, manifested by the lower current i 1 of OPA (Figure a).…”

J. Heyrovský, Japan, and Organic Polarography

“…One exception is the behavior of terephthalaldehyde, which is present in aqueous solutions in 15% as the hydrated form. [28] It is often assumed that orthophthalaldehyde exists predominantly in a cyclic form. Combination of polarographic and spectrophotometric data indicated[29] that at 25 o C orthophthaldehyde is present in aqueous solutions in 15% as the unhydrated form, whereas about 8% is present in the acyclic, monohydrated form and about 77% in a cyclic, hemiacetal form.…”

“…Probably one of the earliest studied slowly established equilibria involving organic compounds was the addition of primary amines to carbonyl compounds. [38] More recent studies of the equilibria in reactions of tere‐ and isophthalaldehydes with ammonia and 2‐aminoethanol[28d] indicated that the equilibrium constant for the formation of an imine for the reaction with 2‐aminoethanol is by three orders of magnitude larger than that of the corresponding reaction with ammonia.…”

“…In solutions of orthophthalaldehyde (OPA), which in aqueous solutions exists not only as the free aldehyde, as the acyclic monohydrate, but also in a cyclic hemiacetal form,[28,29] the rate of its hydration is controlled by the rate of addition of water to the dialdehydic form, but the rate of dehydration depends on the rate of opening of the cyclic hemiacetal form. The increase of limiting current at pH < 2 is due to an acid‐catalyzed dehydration, the increase of current at pH > 7 to a general base‐catalyzed dehydration.…”