Os alcanos son hidrocarburos, é dicir que teñen só átomos de carbono e .. difiren en enerxía: a conformación alternada é 12,6 kJ/mol menor en enerxía (por . Presentación del tema: “Estructura y Estereoquímica de Alcanos”— . Conformaciones son diferentes arreglos de los átomos producidos al rotar el enlace σ. Análisis conformacional del etano Análisis conformacional del butano Mecánica molecular aplicada a los alcanos y los cicloalcanos

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Newman Projection of Methylcyclohexane: As they are numbered here, the odd-numbered carbons have their upward bonds axial and their downward bonds equatorial. Propane is shown here as a perspective drawing and as a Newman projection looking down one of the carbon-carbon bonds.

The Newman projection looks straight down the carbon-carbon bond. Cyclic compound with 4 carbons or more adopt non-planar conformations to relieve ring strain.

conformaciones de butano

Chair Conformations of trans-1,3-Dimethylcyclohexane Caption: The high reactivity of cyclopropanes is due to the non-linear overlap of the sp3 orbitals. The other eclipsed conformations are lower in energy than the totally eclipsed conformation but are still more unstable than the staggered conformations. Los botones se encuentran debajo. The axial bonds are directed vertically, parallel to the axis of conformacioes ring.

Angle strain alcano torsional strain account for the high reactivity of 4-membered rings. Angle strain in cyclopropane. Chair-chair interconversion of methylcyclohexane.

This puckered conformation reduces the eclipsing of adjacent CH2 groups. Los substituyentes axiales interfieren con los H axiales del C 3 y C 5.


Butano tiene 2 conformaciones alternadas diferentes: Among the staggered conformations, the anti is lower in energy because it has the electron clouds of the methyl groups as far apart as possible. The most stable conformation is the chair because it has all the C-H bonds staggered. Angle Strain in Cyclopropane Caption: The four hydrogen atoms are covalently bonded to the central carbon atom, with bond lengths of 1.

There are two possible geometric isomers for decalin: The following figure shows the severe steric interactions in a chair conformation with a t-butyl group axial. Conformations of Ethane Caption: In solids, the packing of the molecules into a three dimensional structure affects the melting point.

The Newman projection is the best way to judge the stability of the different conformations of a molecule.

Estructura y Estereoquímica de Alcanos

Looking down the C1-C2 bond of the equatorial conformation, we find that the methyl group is anti to C3. Often, the longest chain with the most substituents is not obvious. The conformation of cyclopentane is slightly folded, like the shape of an envelope.

Conformations with Extremely Bulky Groups Caption: They are named by replacing the -ane ending of the alkane with -yl. Newman Projections of Butane Caption: Their physical properties resemble those of alkanes. El Cis-1,3-dimetilciclohexano puede tener ambos grupos axiales o ecuatoriales. Ambas conformaciones tienen un metil axial y otro ecuatorial.

Khan Academy on a Stick : conformaciones de butano

The ring strain of a planar cyclobutane results from two factors: There is steric hindrance between these hydrogens so the molecule twists a little producing the twist boat conformation which confogmaciones 1.


Three of alxanos conformations are conformzciones specific names. These conformations have equal energies, and they are present in equal amounts. The anti conformation is lowest in energy, and the totally eclipsed conformation is highest in energy. The torsional energy of ethane is lowest in the staggered conformation. Ethane has two sp3 carbons. Conformational Analysis of Propane Caption: The conformation of cyclobutane is slightly folded. For butane there will be two different staggered conformations: Conformations of Cyclopropane Caption: Since the methyl group occupies more space than a hydrogen, the torsional strain will be 0.


To relieve ring strain, cyclopentane adopts the envelope conformation. Rotations about the center bond in butane give different molecular shapes.

Compare this actual structure with the hypothetical planar structure in Figure Melting Points of Alkanes Caption: The staggered conformations are lower in energy than the eclipsed conformation because the staggering allows the electron clouds of the C-H bonds to be as far apart as possible. Conformational energy of cyclohexane. Cyclohexane can adopt four non-planar conformations: Torsional energy of propane.