NMR Experiments on Acetals: XXIX. The Ease of Acetonide Formation of Some Glycols

Abstract

The ease of acetonide formation for some 1,2-and 1,3-glycols is mzasured and in the discussion of the equilibrium data (tables I and 11). obtained by quantitative evaluation as a function of temperature, emphasis is placed upon the pronounced entropy decrease, and its consequence in the interpretation. All cyclizations are found to be favoured by enthalpy decreases but are governed by entropy changes.The studies on the conductivity of boric acid in the presence of glycols, and the studies on chemical equilibration of these glycols with acetone by Boeseken [l] may be considered as the start of conformational information on heterocyclic compounds. Since then, these and other results, have been used to correlate constitution and conformation with reactivity, and such aspects were of a fundamental nature for the study of natural polyhydroxylic compounds. It is therefore surprising to find rather scarce information with respect to detailed thermodynamic parameters which govern the acetalization. It is obvious, that in order to obtain substantial information, it does not suffice to rely upon observed equilibrium states obtained at one temperature only.We began the study of acetal cyclization by a reinvestigation of the acetonide formation of several glycols and the determination of the equilibrium states as a function of temperature by quantitative nmr spectroscopy. The data obtained for mixtures of acetone and glycols are gathered in tables I and 11. DISCUSSION OF THE TABLES General Aspects1. Although all the reactions are favoured by a decrease of enthalpy, they all are characterized by unfavorable entropy changes. This is not unexpected because during cyclization a diol molecule is replaced by a more associated water molecule.Therefore the gross portion of the observed entropy decrease must be attributed to the concurrent decrease in translational freedom. Those rare reactions which occur almost isoentropically are probably characterised by an increase of rotational and/or vibrational freedom. All discussions on entropy changes in this paper are of comparative nature, and cannot be done on an absolute basis. One of the most striking features, especially when one limits the discussion to a homologous series, is the nearly constant ratio of AH" versus ASo (tableII, nosl,

Benchmark thermodynamic properties of 1,3-propanediol: Comprehensive experimental and theoretical study

“…Having now the evaluated enthalpy of formation of 1,3-propanediol (table 4) together with the literature data for 2,2-dimethyl-1,3-dioxane (CAS 695-30-7) D f H m (l) = À(468.9 ± 2.1) kJ Á mol À1 [52], acetone D f H m (l) = À(248.1 ± 0.7) kJ Á mol À1 [48], and water D f H m (l) = À(285.83 ± 0.04) kJ Á mol À1 [27], we calculated D r H m = À(24.8 ± 3.1) kJ Á mol À1 for the reaction (10). A fair agreement between the experimental reaction enthalpy by Anteunis et al [49] and our estimate increase the confidence of the extended dataset for acetals and ketals measured in this laboratory.…”

“…Moreover, we can apply the value of D f H m (l) for evaluation of the experimental results available in the literature. For example, a very interesting series of equilibrium studies of acetals and ketals were published by Anteunis et al [49,50]. Reviewing these studies in the previous work [51], it was not possible to assess reliability of the reaction enthalpy D r H m = -(23.0 ± 1.5) kJ Á mol À1 [49] measured by using the NMR-spectroscopy for the following reaction: …”

Bio-Based Solvents and Gasoline Components from Renewable 2,3-Butanediol and 1,2-Propanediol: Synthesis and Characterization

“…The ketalization between diols and acetone (or MEK) should comply with the general rules known for the reactions of this type. As is known, the ketalization process is slightly exothermic and results in a decrease in entropy [47]. Thus, to obtain the maximum ketal yields lower temperatures are preferred.…”

A Wide Range of Flavoring–Carrier Fluid Adducts Form in E-Cigarette Liquids

“…While some acetals formed from aldehyde flavorings have been identified, there may also be other non-aldehyde based flavoring molecules that can undergo reactions in e-liquids. Ketones are not as reactive as aldehydes but are able to undergo analogous reactions . One example of ketalization is the reaction of acetoin, a known e-liquid flavoring, with PG .…”