Helicoid shiftamers.

Area of Science:

• Organic Chemistry
• Computational Chemistry
• Polymer Science

Background:

• Helical polyenes are complex organic molecules with unique structural properties.
• Hydrogen shifts are fundamental reactions in organic chemistry, influencing molecular transformations.
• Understanding reaction mechanisms in polyenes is crucial for designing new materials and catalysts.

Purpose of the Study:

• To calculate activation barriers for antarafacial [1,7]-hydrogen shifts in helical polyenes.
• To investigate the influence of saturated substructures on these hydrogen shifts.
• To predict the hydrogen shift barrier in an infinite polyene system ([1,7]-shiftamer).

Main Methods:

• Computational chemistry methods were employed to model and calculate activation barriers.
• Density Functional Theory (DFT) was likely used for electronic structure calculations.
• Analysis focused on the transition states of [1,7]-hydrogen shifts in various helical polyene models.

Main Results:

• Activation barriers for antarafacial [1,7]-hydrogen shifts were determined for several helical polyene systems.
• The presence of saturated substructures was found to influence the calculated barriers.
• A significantly low activation barrier of approximately 14 kcal/mol was predicted for the [1,7]-shiftamer.

Conclusions:

• Antarafacial [1,7]-hydrogen shifts in helical polyenes are feasible, with barriers dependent on conformation.
• Preorganization into a helical conformation is key to lowering the activation barrier.
• The [1,7]-shiftamer represents a model system with a remarkably accessible hydrogen shift pathway.