4. Alkanes Flashcards
An aliphatic hydrocarbon having only C─C and C─H σ bonds.
Alkanes
A compound made up of only the elements of carbon and hydrogen.
Hydrocarbons
A compound with the general formula CnH2n + 2. They contain the maximum number of hydrogen atoms per carbon.
Acyclic Alkane (Saturated Hydrocarbons)
A compound that contains carbons joined in one or more rings. With one ring have the general formula CnH2n.
Cycloalkane
Two different compounds that have the same molecular formula.
Isomers
Two compounds that have the same molecular formula, but differ in the way the atoms are connected to each other.
Constitutional Isomers (Constitutional Isomer)
An acyclic alkane that has all of its carbons in a row.
Straight-Chain Alkane (Normal Alkane)
An acyclic alkane that has alkyl substituents bonded to the parent carbon chain.
Branched-Chain Alkane
A CH2 group bonded to a carbon chain (─CH2─) or part of a double bond (CH2═).
Methylene Group
A group of compounds that differ by only a CH2 group in the chain.
Homologous Series
A systematic method for naming compounds developed by the International Union of Pure and Applied Chemistry.
IUPAC System of Nomenclature
The name of a molecule indicating the compound’s chemical structure. The systematic name is also called the IUPAC name.
Systematic Name
The portion of the IUPAC name of an organic compound that indicates the number of carbons in the longest continuous chain in the molecule.
Parent Name
A group formed by removing one hydrogen from an alkane. Alkyl groups are named by replacing the suffix -ane of the parent alkane with -yl.
Alkyl Group
A group or branch attached to the longest continuous chain of carbons in an organic molecule.
Substituent
If the number of the carbons in the ring is greater than/equal to the number of carbons in the longest chain.
Naming a compound as a Cycloalkane
The name of a molecule that was adopted prior to and therefore does not follow the IUPAC system of nomenclature.
Common Names
A fossil fuel containing a complex mixture of compounds, primarily hydrocarbons with 1 to 40 carbon atoms.
Petroleum
The three-dimensional structure of molecules.
Stereochemistry
The different arrangements of atoms that are interconverted by rotation about single bonds.
Conformations
A conformation of a molecule where the bonds on one carbon are directly aligned with the bonds on the adjacent carbon.
Eclipsed Conformation
A conformation of a molecule in which the bonds on one carbon bisect the R─C─R bond angle on the adjacent carbon.
Staggered Conformation
The angle that separates a bond on one atom from a bond on an adjacent atom.
Dihedral Angle
An end-on representation of the conformation of a molecule. The Newman projection shows the three groups bonded to each carbon atom in a particular C–C bond, as well as the dihedral angle that separates the groups on each carbon.
Newman Projection
The energy difference between the staggered and eclipsed conformations of a molecule.
Torsional Energy
An increase in the energy of a molecule caused by eclipsing interactions between groups attached to adjacent carbon atoms.
Torsional Strain
An increase in energy resulting when atoms in a molecule are forced too close to one another.
Steric Strain
The energy difference between the lowest and highest energy conformations of a molecule.
Barrier to Rotation
An increase in the energy of a molecule resulting when the bond angles of the sp3 hybridized atoms deviate from the optimum tetrahedral angle of 109.5°.
Angle Strain
A stable conformation adopted by cyclohexane that resembles a chair that results from the elimination of angle strain (all C─C─C bond angles are 109.5°) and torsional strain (all groups on adjacent carbon atoms are staggered).
Chair Conformation of Cyclohexane
Bonds located above or below and perpendicular to the plane of the chair conformation of cyclohexane. Three axial bonds point upwards (on the up carbons) and three axial bonds point downwards (on the down carbons).
Axial Bonds
Bonds located in the plane of the chair conformation of cyclohexane (around the equator). Three equatorial bonds point slightly upwards (on the down carbons) and three equatorial bonds point slightly downwards (on the up carbons).
Equitorial Bonds
A stepwise process in which one chair conformation of cyclohexane interconverts with a second chair conformation.
Ring-Flipping
An unstable conformation adopted by cyclohexane that resembles a boat. The instability of the boat conformation results from torsional strain and steric strain. The boat conformation of cyclohexane is 30 kJ/mol less stable than the chair conformation.
Boat Conformation of Cyclohexane
Hydrogens in the boat conformation of cyclohexane that are on either end of the “boat” and are forced into close proximity to each other.
Flagpole Hydrogens
A steric interaction between two axial substituents of the chair form of cyclohexane. Larger axial substituents create unfavorable 1,3-diaxial interactions, destabilizing a cyclohexane conformation.
1,3-Diaxial Interaction
Two isomers that differ only in the way the atoms are oriented in space.
Stereoisomers
An isomer of a ring or double bond that has two groups on the same side of the ring or double bond.
Cisisomer
An isomer of a ring or double bond that has two groups on opposite sides of the ring or double bond.
Transisomer
A process that results in a loss of electrons. For organic compounds, oxidation results in an increase in the number of C─Z bonds or a decrease in the number of C─H bonds; Z = an element more electronegative than carbon.
Oxidation
A process that results in the gain of electrons. For organic compounds, reduction results in a decrease in the number of C─Z bonds or an increase in the number of C─H bonds; Z = an element more electronegative than carbon.
Reduction
An oxidation–reduction reaction, in which an alkane or other organic compound reacts with oxygen to form CO2 and H2O, releasing energy.
Combustion
A biomolecule with a large number of C─C and C─H σ bonds that is soluble in organic solvents and insoluble in water.
Lipids
