Crystal packing in vicinal diols CnHm(OH)2.

Area of Science:

• Crystallography
• Supramolecular Chemistry
• Organic Chemistry

Background:

• Intermolecular interactions, particularly hydrogen bonds, are crucial in determining the solid-state structures of organic molecules.
• Vicinal diols (compounds with two hydroxyl groups on adjacent carbon atoms) are versatile building blocks with potential for extensive hydrogen bonding.

Purpose of the Study:

• To investigate the hydrogen bonding patterns of vicinal diols using crystallographic data.
• To correlate hydrogen bonding extent with molecular structure, crystal symmetry, and packing efficiency.

Main Methods:

• Analysis of crystal structures from the Cambridge Structural Database.
• Statistical analysis of hydrogen bond motifs, space group frequencies, and unit cell parameters.

Main Results:

• Approximately 50% of studied vicinal diols form extensive intermolecular O-H...O networks, often featuring high-symmetry space groups and increased molecular multiplicity (Z' > 1).
• The R(2)(2)(10) dimer is a common motif in fully hydrogen-bonded structures, enabling the formation of 1D, 2D, and 3D supramolecular assemblies.
• The remaining vicinal diols predominantly form simple O-H...O chains, with less exceptional space group distributions.
• The degree of substitution of the vicinal diol is the primary factor governing the extent of O-H...O bond formation.

Conclusions:

• The extent of intermolecular O-H...O bonding in vicinal diols is strongly dependent on their substitution pattern.
• While hydrogen bonding can lead to ordered structures, it can also hinder efficient space filling due to conflicting spatial requirements.