Structure Systematics of Auxin Herbicides. XXX. The Crystal Structures of (2-Isopropylphenoxy)-acetic Acid, (4-Fluorophenoxy)acetic Acid, (2,4-Dichloro-5-fluorophenoxy)acetic Acid and (Indol-3-ylthio)acetic Acid

Abstract

The crystal structures of four analogues of the auxin herbicide series, including inactive examples, have been determined by X-ray diffraction methods. The compounds (2-isopropy1phenoxy)acetic acid (1), (4-fluorophenoxy)acetic acid (2) and (2,4-dichloro-5-fluorophenoxy)acetic acid (3) are from the phenoxyalkanoic acid series while (indol-3-ylthio)acetic acid (4) is the sulfur analogue of the natural plant hormone indole-3-acetic acid. All examples exist as hydrogen-bonded cyclic dimers [O…O, 2.640(7), 2.62(1), 2.637(4) and 2.665(4) � for (1)-(4), respectively]. Compounds (1) and (2) are essentially planar while compounds (3) and (4) have side chains anticlinally related to the ring systems, similar to (2,4-dich1orophenoxy)acetic acid and to indole-3-acetic acid.

Crystal structures and hydrogen bonding in the morpholinium salts of four phenoxyacetic acid analogues

“…The conformation of the oxoacetate side chains in the anions of (I) and (II) are essentially planar, with the defining torsion angle C1A-O11A-C12A-C13A = 176.75 14and 176.53 (14) , respectively. This antiperiplanar (180AE30 ) conformation is similar to those of the parent acids PAA (À175.1 ; Kennard et al, 1982), PFPA [176.0 (6) ; Smith et al, 1992] and their proton-transfer salts, e.g. the ammonium salts of PAA [À177.48 (18) ] and PFPA [À178.98 (17) ] (Smith, 2014).…”

Synthesis, crystal structure elucidation, Hirshfeld surface analysis, 3D energy frameworks and DFT studies of 2-(4-fluorophenoxy) acetic acid

“…The compound obtained was characterized spectroscopically, and the structure was confirmed by X-ray diffraction studies. The crystal structure characterization of the title compound was previously reported by Smith et al [30]. Hirshfeld surface analysis and DFT study of the title compound were presented in this article.…”

Two-dimensional coordination polymeric structures in the sodium, potassium and rubidium complex salts with (4-fluorophenoxy)acetic acid

“…The comparative conformational features of the (4-fluorophenoxy)acetate ligands in (I)-(III) are similar, with the phenoxyacetate side chain essentially coplanar with the benzene ring, with the defining torsion angles C6-C1-O11-C12, C1-O11-C12-C13 and O11-C12-C13-O14 being À167.6 (3), 170.2 (2) and À167.2 (2) for (I), 180.0 (5), À174.1 (5) and À167.0 (5) for (II), and 178.2 (4), À176.3 (4) and À170.1 (4) for (III). In the parent acid PFPA (Smith et al, 1992) and as a ligand in its metal complex structures (e.g. O'Reilly et al, 1984;Smith, 2012), it adopts similar antiperiplanar conformations.…”

“…The structures of the parent acid PFPA (Smith et al, 1992), the ammonium salt (Smith, 2014) and the morpholinium salt (Smith & Lynch, 2015) are also known. In the metal complex examples, with the exception of the Mg compound, in which the cation is the hexaaquamagnesium species with the PFPA anions uncoordinated, coordination involves the carboxylate group in either a monodentate bridging or a bidentate chelate mode or together with the phenoxy O-atom donor in a The structures of the alkali metal complex salts (Li, Rb and Cs) with 2,4-D (Smith, 2015a), a second Cs-2,4-D complex (Smith & Lynch, 2014) and the K + and Rb + salts of isomeric 3,5-D (Smith, 2015b) are known, but the structure of the anhydrous Cs + complex salt (Smith & Lynch, 2014) represents the only reported alkali metal salt with PFPA.…”