Crystal structure of (E)-undec-2-enoic acid

Area of Science:

• Organic Chemistry
• Crystallography
• Molecular Structure

Background:

• Understanding the molecular arrangement and intermolecular forces in organic compounds is crucial for predicting their physical properties.
• Carboxylic acids, particularly unsaturated variants, exhibit diverse crystal packing influenced by their functional groups and alkyl chains.

Purpose of the Study:

• To elucidate the crystal structure and molecular conformation of a specific low-melting α,β-unsaturated carboxylic acid (C11H20O2).
• To analyze the geometric relationship between the octyl chain and the acrylic acid fragment within the crystal lattice.

Main Methods:

• Single-crystal X-ray diffraction was employed to determine the three-dimensional structure.
• Least-squares refinement was used to establish the precise atomic coordinates and bond parameters.
• Analysis of hydrogen bonding and crystal packing was performed.

Main Results:

• The molecule features an octyl chain with a specific orientation relative to the acrylic acid fragment.
• The octyl chain's mean line forms a 60.10(13)° angle with the normal to the acrylic acid plane.
• Centrosymmetric molecules form dimers via O-H⋯O hydrogen bonds, creating layered structures parallel to the (041) plane.

Conclusions:

• The crystal structure reveals a defined conformation of the unsaturated carboxylic acid, influenced by the octyl chain.
• Intermolecular hydrogen bonding dictates the formation of dimers and layered packing in the solid state.
• The findings contribute to the understanding of structure-property relationships in unsaturated carboxylic acids.