Transformation of boric acid with hydroxyl-containing compounds in the solid-phase system

Abstract

Boron is one of the major microelements for normal growth, vital functions, and reproduction of plants. Plants require Boron during all life, because it participates in the regulation of the growth of reproductive organs, in the transport of carbohydrates, in particular sugars, synthesis of cellular walls, increases intensity of photosynthesis, improves a carbohydrate, nucleic and protein exchange, activates enzymes function, positively influences on the processes of fission. The deficit of boron leads not only to the decreasing of agricultural crops but also to the impairment of its quality. It is considered, that in soils and plants boron migration is going in the form of (BO)4–3-, anion, which is going from boron soluble form of boron-containing manures. There is shown that the plants' boron assimilation goes better with a presence in boron-containing compounds carbohydrate residues, alcohols, or when boron is a part of complex anions.

For the improvement and providing of desirable properties of manures, the new boron-containing compounds are synthesized. Nowadays the most prevailing new age boron-containing manure is borateanolamine. It has high solubility and high total content of boron. As we suppose, Boron is contained in manures in more completely plants-assimilated form.

Boric acid has well-expressed ability to create complexes with diol groups, which are in cis-positions. Carbohydrates, higher alcohols, phenols and some hydroxyl-containing compounds belong to groups with the cis-position order. However, boric complexes with those compounds are low stable. For researching those transformations there is important to study the influence of the reaction terms to the boric acid ability to create complex anions with hydroxyl-containing compounds.

During the reaction of boric acid and hydroxyl-containing compounds in the solid-phase system the complex chemical transformations go, when different intermediate compounds are appearing and disappearing. They cannot be selected or revealed by ordinary chemical methods because of instability and a short time of existence.

We used the method of IR spectroscopy for identifying such intermediate compounds, in order to establish regularities in reactions.

We tested pill samples of compounds in the ratio 1 mg of substance to 200 mg of KBr. IR spectres were registered by spectrometer Perkin Elmer Spectrum one FT-IR Spectrometer (300-4000 см-1).

As we compare IR spectres of the original compound and boric acid, we can see a sharp decrease (reduction) of the absorption graph intensities. They correspond to O-H oscillations in boric acid (3212, 2265, 1198, 1471 та 1414 см-1). Thus, we may assume weak interaction of boric acid and D-manit, with creating complex ion, when we rub the compound with room temperature.

The comparative analysis of IR spectres of products from (I series of experiments) and (II series of experiments) shows that the process of the reaction of boric acid and D-sorbit goes with some differences. Based on the apparition of absorption graph on 952 см-1 in a product (I series of experiments), we may say that at these terms the reaction with boric acid and D-sorbit goes through the intermediate formation of four-coordinated boron complex. As we see at (II series of experiments), there is no such absorption graph in IR spectre. That may say about another type of boric acid transformation.

Using IR spectroscopy we may see than boric acid differs in processes of transformations with hydroxyl-containing compounds in the solid-phase system in different condition.

Using IR spectroscopy we may ostend that creating the reaction of the complex ingredient in the solid-phase system is observing already at room temperature.

Using IR spectroscopy proved, that on the formation of an intermediate complex ingredient is affected the molar ratio of reagents.

Interaction reaction of boric acid and hydroxyl-containing compounds normally happened in an aqueous solution with sulfuric acid as a catalyst. Molecular mobility in solution is high, so the probability of clashing of diol groups in cis-positions is quite high.

In case of the solid-phase system, molecular mobility is limited. The large surface allocation and half-homogenization of compound obstruct the molecular interaction. Instead, increasing temperatures accelerate the reaction, and evaporation of water essentially shifts the balance of the reaction to the creation of the final (end) product.

Reagents of the investigated reaction systems have low melting temperatures, so increasing temperatures leads to a softening of compounds and smelting of reagents. In fact, the interaction is in the melt, where interphases borders are missing, and molecular mobility increases.

So, the availability of using the solid-phase system for synthesis of boron-organic esters is shown there. Establishment of boron-containing compounds structure requires successive research.