|
Nomenclature of
cycloalkanes
Cycloalkanes are alkanes with their
carbon atoms arranged in a ring. The general molecular formula for
a cycloalkane is CnH2n.
Cycloalkanes are named by adding the
prefix “cyclo” to the alkane name that signifies the number of carbon
atoms in the ring.
Ring strain
We
know that, ideally, an hybridized carbon has bond angles of 109.5°. The
angles in an equilateral triangle are 60°. The bond angles in cyclopropane,
therefore, are compressed from the ideal bond angle of 109.5° to 60°, a 49.5°
deviation. This deviation of the bond angle from the ideal bond angle causes
strain called angle strain.
Conformations of Cyclohexane
The cyclic compounds most commonly found in nature contain six-membered
rings because such rings can exist in a conformation that is almost completely
free of strain. This conformation is called the chair conformation.
Cyclohexane can also
exist in a boat conformation. The boat conformer is not as stable as
the chair conformer because some of the bonds in the boat conformer are eclipsed,
giving it torsional strain. The boat conformer is further destabilized by the
close proximity of the flagpole hydrogens, which causes steric strain.
Substituted Cyclohexanes:
1,3-diaxial interactions
Cyclohexane rapidly interconverts between two
stable chair conformations This interconversion is known as ring flip. When the
two chair conformers interconvert, bonds that are equatorial in one chair
conformer become axial in the other chair conformer
|
Glucosa
Es el compuesto orgánico más abundante
en la naturaleza y la principal fuente
de energía de las células.
Fructosa
Azúcar que se encuentra en las frutas
y en la miel. |