Angle strain

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Angle strain

The presence of angle strain in a molecule

Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
indicates that in a specific chemical conformation there exist bond angles that deviate from the ideal bond angles required to achieve maximum bond strength. Maximum bond strength results from effective overlap of atomic orbital

Atomic orbital

An atomic orbital is a mathematical function that describes the wave-like behavior of an electron in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus....
s in a chemical bond

Chemical bond

A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds....
.

Angle strain typically affects cyclic molecules because non-cyclic molecules will thermodynamically

Thermodynamics

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The presence of angle strain in a molecule

Molecule

Atomic orbital

Chemical bond

Thermodynamics

In physics, thermodynamics is the study of the conversion of heat energy into different forms of energy ; different energy conversions into heat energy; and its relation to macroscopic variables such as temperature, pressure, and volume....
conform to the most favorable stable state. Angle strain in cyclic molecules is also called Baeyer strain
Baeyer strain theory

Baeyer strain theory or strain theory explains specific behaviour of chemical compounds in terms of bond angle strain.It was proposed by Adolf von Baeyer in 1885 to account for the unusual reaction rate in ring opening reactions of cyclopropanes and cyclobutanes where this angle strain is relieved....
.

As an example of angle strain, take cyclic alkanes, in which each carbon is equally bonded two carbons and two hydrogens. Since each of the four bonds of a carbon is equivalent, it is sp³ hybridized and ideally should have cos^-1(-1/3) ˜ 109.5° (the angle that maximizes the distance between atoms) bond angles. Due to the limitations of cyclic structure, however, the ideal angle is only achieved in a six carbon ring - cyclohexane

Cyclohexane

Cyclohexane is a cycloalkane with the molecular formula Carbon6Hydrogen12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which are intermediates used in the production of nylon....
, and only when it is in its chair conformation. For other cyclic alkanes, the bond angles deviate from ideal. In cyclopropanes (3 carbons) and cyclobutanes (4 carbons) the C-C bonds will be 60° and ~90° respectively.

A quantitative measure for angle strain is strain energy

Strain energy

In a molecule, strain energy is released when the constituent atoms are allowed to rearrange themselves in a chemical reaction or a change of chemical conformation in a way that:...
. Having higher angle strain makes a molecule more unstable and reactive.

Angle strain and torsional strain combine to create ring strain

Ring strain

Ring strain is an organic chemistry term that describes the destabilization of a cyclic molecule?such as a cycloalkane?due to the non-favorable high energy Molecular geometry of its atoms....
that affects cyclic molecules.

Examples of molecules with angle strain cycloalkane

Cycloalkane

Cycloalkanes are types of alkanes which have one or more rings of carbon atoms in the chemical structure of their molecules. Alkanes are types of Organic compound hydrocarbon Chemical compound which have only single chemical bonds in their chemical structure....
s, cyclophane

Cyclophane

A cyclophane is a hydrocarbon consisting of an aromatic unit and an aliphatic Chain that forms a bridge between two non-adjacent positions of the aromatic ring....
s, platonic hydrocarbons

Platonic hydrocarbons

Platonic hydrocarbons are the molecule representation of platonic solid geometries with vertices replaced by carbon atoms and with edges replaced by chemical bonds....
and pyramidal alkene

Pyramidal alkene

Pyramidal alkenes are alkenes in which the two carbon atoms making up the double bond are not coplanar with their four substituents . This deformation from a trigonal planar geometry to a tetrahedral molecular geometry is the result of angle strain induced in the molecule due to geometric constraints....
s.

Examples

cyclopropane
Cyclopropane

Cyclopropane is a cycloalkane molecule with the molecular formula C3H6, consisting of three carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms....
, C₃H₆
ethylene oxide
Ethylene oxide

Ethylene oxide is the organic compound with the chemical formula C2H4O. This colorless flammable gas with a faintly sweet odor is the simplest epoxide, a three-membered ring consisting of two carbon and one oxygen atom....
CH₂OCH₂
chemiluminescence of CSPD
Chloro-5-substituted adamantyl-1,2-dioxetane phosphate

CSPD or disodium 3-phenyl phosphate or Chloro-5-substituted adamantyl-1,2-dioxetane phosphate is a reagent that is used in enhanced chemiluminescence ELISA kits....