Chapter 2 - Alkanes And Cycloalkanes Flashcards
Compounds that only contain C and H atoms.
Hydrocarbons
Carbon-carbon single bonds
Saturated
Carbon-carbon multiple bonds
Unsaturated
Special class of cyclic compounds related in structure to benzene.
Aromatic
o Hydrocarbon single bonds
o Acyclicalkanes
Alkanes
General formula for Alkanes
CnH2n+2
Bond angle of alkanes
109.5 degrees (sp3 hybridized)
Simplest Alkane
Methane (CH4)
Meaning of IUPAC
International Union of Pure and Applied Chemistry
True or False:
Alkanes are
- soluble in water
- nonpolar
- have higher boiling points
False
(Insoluble, nonpolar, lower boiling points)
Strongest intermolecular forces
Hydrogen bonding
Interconvertible by rotation around a single bond
Conformations
Stereoisomers where atoms are connected in the same order but arranged differently in space
Conformers
Staggered and eclipsed conformations of ethane
Rotamers
It is the most stable (lowest potential energy) of all ethane conformations
Staggered conformation
It is the least stable (highest potential energy) of all ethane conformations
Eclipsed conformation
Molecular formula for cycloalkanes
CnH2
• Smallest ring structure possible
• Rigid and very highly strained (more reactive) as the
bond angles (60 degrees) are distorted from ideals
(109.5 degrees)
Cyclopropane
• “puckered” conformation
• More flexible than cyclopropane and not flat
• More reactive than a linear alkane
Cyclobutane
• “envelope’ conformation
• Less strained
• More flexible than cyclobutene
• Bond angle ~105 degrees
Cyclopentane
• “Chair” conformation
• Highly flexible
• Can adopt a strain free non-planar conformation with
bond angle of 109.5
Cyclohexane
It is where all equatorial H become axial and axial become equatorial
Ring inversion or “chair-chair” flip
Substituents are on the opposite side
Trans
Substituents are on the same side
Cis
• Contain carbon atoms arranged in a ring.
• Named by adding the prefix cyclo-
Cycloalkanes
The attractive forces that exist between molecules.
Intermolecular forces
What is the order of increasing strength (intermolecular forces)
a. dipole-dipole interactions
b. hydrogen bonding
c. london dispersion forces
c, a, b
forces are very weak interactions due to the momentary changes in electron density in a molecule.
London dispersion
True or False:
Not all covalent compounds exhibit London dispersion forces.
False
(All exhibit this type)
True or False:
The larger the molecule, the larger the attractive force, and the stronger the intermolecular forces.
True
Attractive forces between the permanent dipoles of 2 polar molecules
Dipole-dipole
Hydrogen bonding occurs when a hydrogen atom is bonded to what atoms? (3)
O, N, or F
Shows the interconversion via a 60° rotation about the C-C bond, as shown by the curved arrows
Sawhorse drawing
An end-on view down the C-C axis.
Newman projection
Type of Stereoisomer:
both group are located on the same side of the conformation. two groups can be on axial or in equatorial position
Trans stereoisomer
Type of stereoisomer:
two groups are located on the opposite side of the conformation. One is on axial position and the other group is on equatorial position.
Cis stereoisomer
Substitution reaction in which a chlorine atom is substituted for a hydrogen atom.
Chlorination
Substitution reaction in which a bromine atom is substituted for a hydrogen atom.
Bromination
What do you call the products when excess halogen is present?
Polyhalogenated products
What do you call the product of an unsubstituted cycloalkanes?
Single and pure organic product
Halogenation occurs via what reaction?
free-radical chain of reactions.
Steps for the free-radical chain mechanism of halogenation (3)
➢ chain-initiating step,
➢ chain-propagating steps
➢ chain-terminating steps
