Download Wade03 estructura y estereoquimica de alcanos . leccin 5. alcanos y cicloalcanos – orgnica 2 leccin 5. Documents. estereoquímica introducción los isómeros estructurales se definen como isómeros, todos aquellos compuestos químicos que poseen igual fórmula global, . Estereoquímica es el término aplicado a los aspectos tridimensionales de la estructura CAPÍTULO TRES Conformaciones de alcanos y cicloalcanos.
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The different arrangement formed by rotations about a single bond are called conformations, and a specific is called conformer.
This puckered conformation reduces the eclipsing of adjacent CH2 groups. Listed in Table 3. Their physical properties resemble those of alkanes. When looking for the longest continuous chain, look to find all the different chains of that length.
There is steric hindrance between these hydrogens so the molecule twists a little producing the twist boat conformation which is 1. The equatorial bonds are directed outward, toward the equator of the ring. When molecules can pack in neat order avoiding empty pockets the melting point will be higher than when the packing is not ordered.
Angle strain and torsional strain account for the high reactivity of 4-membered rings. Ethane, the two-carbon alkane, is composed of two methyl groups with overlapping sp3 hybrid orbitals forming a sigma bond between them.
An equatorial methyl group will be anti to the C3.
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Puckered conformer reduces torsional strain. The more stable conformation has both methyl groups in equatorial positions. The eclipsed conformation is about 3. Home Education Wade03 alfanos y estereoquimica de alcanos. All the carbon-carbon bonds are eclipsed, generating torsional strain that contributes to the total ring strain. First in alphabet cicooalcanos lowest number. Chair interconversion would still produce an axial and an equatorial methyl.
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.
Estructura y Estereoquímica de Alcanos
The most stable conformation is the chair because it has all the C-H bonds staggered. Angles would beif planar. As they are numbered here, the odd-numbered carbons have their upward bonds axial and their downward bonds equatorial. 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.
Rotations about the center bond in butane give different molecular shapes. 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. Conformational Analysis of Propane Caption: The axial bonds are directed vertically, parallel to the axis of the ring. These conformations have equal energies, and they are present in equal amounts.
Ignore di- tri- etc. Conformational Analysis of Butane Caption: The torsional energy of ethane is lowest in the staggered setereoquimica. Chapter 3CyclohexaneCombustion cicloalxanos shows its unstrained.
Cyclobutane adopts the folded conformation to decrease the torsional strain caused by eclipsing hydrogens. To convert between these two conformations, the molecule must pass through the unstable estereoqui,ica conformation.
Alcanos ramificados tienen p. Chapter 3End of Chapter 3Chapter 3. The anti conformation is lowest in energy, and the totally eclipsed conformation is highest in energy.
Ethane has two sp3 carbons. Name the groups attached to the chain, using the carbon number as the locator.
Substituents on a carbon chain are called cicpoalcanos groups. Some conformations can be more stable than others. The conformation of cyclobutane is slightly folded.
At room temperature, this estereoquimic is easily overcome, and the molecules rotate constantly. 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. Solution The longest carbon chain contains eight carbon atoms, so this compound is named as an octane.
Alcanos y Cicloalcanos by Adrian Marcelo Giurno on Prezi
The Newman projection is the best way to judge the stability of the different conformations of a molecule. Conformations of Cyclopropane Caption: Conformations of Cyclohexane Caption: The bond angles are Conformations with Extremely Bulky Groups Caption: Conformational Energy Diagram of Cyclohexane Caption: Longer chained alkanes have greater surface area and can have more surface contact and more induced dipoles than branched alkanes with smaller surface areas.
Cyclohexanes with tertiary-butyl substituents show that an axial t-butyl group is severely hindered.