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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When looking for the longest continuous chain, look to find all the different chains of that length. The even-numbered carbons have their confrmaciones bonds axial and their upward bonds equatorial. An equatorial methyl group will be anti to the C3. Because of their smaller surface areas, branched alkanes have lower boiling points than unbranched alkanes.

Khan Academy on a Stick : conformaciones de butano

The high reactivity of cyclopropanes is due to the non-linear overlap of the sp3 orbitals. Viewed from the Newman projection, the chair conformation has no eclipsing of the carbon-carbon bonds.

For butane there will be two different staggered conformations: Conformational Energy Diagram of Cyclohexane Caption: Torsional energy of propane. Chair Conformations of trans-1,3-Dimethylcyclohexane Caption: Alcanos con par de C tienen p. Conformations of Cyclobutane Caption: Groups like tert-butyl are so bulky that it will force the chair conformation where it is in the equatorial position, regardless of other groups present. As they are numbered here, the odd-numbered carbons have their upward bonds axial and their downward bonds equatorial.


The ring strain of a planar cyclobutane results from two factors: In the Newman projection it is easier to see the steric interaction between the methyl substituent and the hydrogens and carbons of the ring.


Their physical properties resemble those of alkanes. Newman Projections of Butane Caption: To make this website work, we log user data and share it with processors. Alcanos ramificados tienen p. 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.

Rotations about the center bond in butane give different molecular shapes. The eclipsed conformation is about 3. Solution The longest carbon chain contains eight carbon atoms, so this compound is named as an octane. All the C-H bonds are staggered in the chair conformation.

Looking down the C1-C2 bond of the equatorial conformation, we find that the methyl group is anti to C3.

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In the actual molecule, the boat conformation is skewed to give the twist boat, a conformation with less eclipsing of bonds and less interference between the two flagpole hydrogens. When molecules can pack in neat order avoiding empty pockets the melting point will be higher than when the packing is not ordered.


Cyclohexane can adopt four non-planar conformations: Los botones se encuentran debajo. The Newman projection is the best way to judge the stability of the different conformations of a molecule.

Alkyl substituents on cyclohexane rings will tend to be equatorial to avoid 1,3-diaxial interactions. Torsional energy of butane.

The unfavorable conformation has both methyl groups in axial positions, with a 1,3-diaxial interaction between them. This puckered conformation reduces the eclipsing of adjacent CH2 groups. La eclipsada es 3. The most stable conformation is the chair because it has all the C-H bonds staggered. The other eclipsed conformations are lower in energy than the totally eclipsed conformation but are still more unstable than the staggered conformations.

Angle strain in cyclopropane. Axial hydrogens are pointed straight up or down, parallel to the axis of the ring. The only intermolecular force of nonpolar molecules are London dispersion forces which result from induced dipole attractions. In the symmetrical boat conformation of cyclohexane, eclipsing of bonds results in torsional strain.

Conformations of Ethane Caption: Conformational Analysis of Ethane Caption: Esta interferencia es llamada interacciones 1,3-diaxial. The following figure shows the severe steric interactions in a chair conformation with a t-butyl group axial.