Influence of Aliphatic Chain Length on Structural, Thermal and Electrochemical Properties of n-alkylene Benzyl Alcohols: A Study of the Odd–Even Effect

Abstract

The century-old, well-known odd–even effect phenomenon is still a very attractive and intriguing topic in supramolecular and nano-scale organic chemistry. As a part of our continuous efforts in the study of supramolecular chemistry, we have prepared three novel aromatic alcohols (1,2-bis [2-(hydroxymethyl)phenoxy]butylene (Do4OH), 1,2-bis[2-(hydroxymethyl)phenoxy]pentylene (Do5OH) and 1,2-bis[2-(hydroxymethyl)phenoxy]hexylene (Do6OH)) and determined their crystal and molecular structures by single-crystal X-ray diffraction. In all compounds, two benzyl alcohol groups are linked by an aliphatic chain of different lengths (CH2)n; n = 4, 5 and 6. The major differences in the molecular structures were found in the overall planarity of the molecules and the conformation of the aliphatic chain. Molecules with an even number of CH2 groups tend to be planar with an all-trans conformation of the aliphatic chain, while the odd-numbered molecule is non-planar, with partial gauche conformation. A direct consequence of these structural differences is visible in the melting points—odd-numbered compounds of a particular series display systematically lower melting points. Crystal and molecular structures were additionally studied by the theoretical calculations and the melting points were correlated with packing density and the number of CH2 groups. The results have shown that the generally accepted rule, higher density = higher stability = higher melting point, could not be applied to these compounds. It was found that the denser packaging causes an increase in the percentage of repulsive H‧‧‧H interactions, thereby reducing the stability of the crystal, and consequently, the melting points. Another interesting consequence of different molecular structures is their electrochemical and antioxidative properties—a non-planar structure displays the highest oxidation peak of hydroxyl groups and moderate antioxidant activity.

Formononetin‐Vitamin E Conjugate Synergistically Supports Adipogenesis, Attenuates Oxidative Stress, and Restores Insulin Sensitization in Differentiated Preadipocytes

“…The range of melting temperature recorded with FMN, VES and VESylated‐FMN are 256–261 °C, 75–79 °C and 65–70 °C respectively (Figure S2). The melting point exhibited by VESylated‐FMN is similar to VES, while lowered to FMN due to the odd number of aliphatic hydrocarbons on VES [16] . This aliphatic hydrocarbon decreases the cumulative strength of intermolecular van der Waals forces followed by melting point.…”

“…The melting point exhibited by VESylated-FMN is similar to VES, while lowered to FMN due to the odd number of aliphatic hydrocarbons on VES. [16] This aliphatic hydrocarbon decreases the cumulative strength of intermolecular van der Waals forces followed by melting point. Interestingly, no endothermic peaks were recorded with VESylated-FMN at temperature range of 256-261 °C and 75-79 °C, suggesting the purity of conjugate.…”

New betulin imine derivatives with antioxidant and selective antitumor activity

“…This behavior is in accordance with the higher ability of a longer chain to disrupt the supramolecular ordering of the compounds, due to the higher conformational disorder which favors the disruption of the Hbonds between the betulin cores, leading to free movement of the molecules in the isotropic state. 57 Moreover, the samples with a shorter length of the aliphatic chain presented a stronger birefringence at room temperature and a sharper crystallineisotropic transition, compared to those with longer aliphatic chains which showed less intense birefringence and a softening behavior in a temperature range of approx. 10 1C (Fig.…”