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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Análisis conformacional by Química Orgánica on Prezi
This conformation is lower in energy and favored over the conformation with the methyl in the axial position. Since the methyl group occupies more coonformaciones than a hydrogen, the torsional strain will be 0. They are named by replacing the -ane ending of the alkane with -yl. Because of congormaciones smaller surface areas, branched alkanes have lower boiling points than unbranched alkanes.
Longer chained alkanes have greater surface area and can have more surface contact and more induced dipoles than branched alkanes with smaller surface areas. Conformations of Cyclobutane Caption: In solids, the packing of the molecules into a three dimensional structure affects the melting point. Numbering from left to right gives the first branch on C2; numbering from right to left gives the first branch on C3, so conformaxiones number from left to right.
Ethane, the two-carbon alkane, is composed of two methyl groups with overlapping sp3 hybrid orbitals forming a sigma bond between them. In the symmetrical boat conformation of cyclohexane, eclipsing of bonds results in torsional strain. Cyclohexane can adopt four non-planar conformations: Looking down the C1-C2 bond of the equatorial conformation, we find alcanox the methyl group is anti to C3.
Alkyl substituents on cyclohexane rings will tend to be equatorial to avoid 1,3-diaxial interactions. The other eclipsed conformations are lower in energy than the totally eclipsed conformation but are still more unstable than the staggered conformations.
Chair Conformations of cis-1,3-Dimethylcyclohexane Caption: Sobre el proyecto SlidePlayer Condiciones de uso. The six-membered rings in cis- and trans-decalin assume chair conformations. The chair conformation of cyclohexane has one methylene group puckered upward and another puckered downward. There are two possible geometric isomers for decalin: Torsional energy of butane.
The methyl group is axial in one conformation, and equatorial in the other. Any carbon with four sigma bonds has an sp3 hybridization.
Compare this actual structure with the hypothetical planar structure in Figure The angle compression for butane is When molecules can pack in neat order avoiding empty pockets the melting point will be higher than when the packing is not ordered. Chair-chair interconversion of methylcyclohexane.
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The melting point curve for n-alkanes with even numbers of carbon atoms is slightly higher than that for alkanes with odd numbers of carbons. The Newman Projection of Propane Caption: Conformational Analysis of Butane Caption: Viewed from the Newman projection, the chair conformation has no eclipsing of the carbon-carbon bonds. Some common alkyl groups and their names.
The most stable conformation is the chair because it has all the C-H bonds staggered. The four hydrogen atoms are covalently bonded to the central carbon atom, with bond lengths of 1. Newman Projection of Methylcyclohexane: Torsional strain in cyclopropane.
The equatorial bonds are directed outward, toward the equator of the ring. La eclipsada es 3. This puckered conformation reduces the eclipsing of adjacent CH2 groups.
Estructura y Estereoquímica de Alcanos
Ethane has two sp3 carbons. Methane is perfectly tetrahedral, with the Torsional kos of propane. In the Newman projection it is easier to see the steric interaction between the methyl substituent and the hydrogens and carbons of the ring.
The bond angles are Alcohols are compounds whose molecules have a hydroxyl.