Chapter 2 Flashcards
What is this style of describing a compound?
Lewis Structure
What is this style of describing a compound?
Partially Condesnsed Structure
C-H bonds are not all drawn explicitly
What is this style of describing a compound?
Condensed Structure
single atoms are not draw and groups of atoms are clustered together (when possible)
What is this style of describing a compound?
Molecular Formula
conveys no structural information
What is a constitutional isomer?
same molecular formula,
different structure
What is this style of describing a compound?
Bond-Line Structures
- each corner is a carbon
- hydrogens are not drawn on carbons
- heteroatoms (not carbon or hydrogen) are drawn
- hydrogens connected to heteroatoms are drawn
define functional group
a functional group is a characteristic group of atoms/bonds that have a predictable chemical behavior
(ex: endorphins, codeine, morphine, heroin)
describe + formal charge
+ formal charge is having more protons in the nucleus than electrons surround it
(always remembering the 1s shell)
describe - formal charge
- formal charge is having more electrons around the atom than protons in the nucleus
(always remembering the 1s shell)
describe how to determine formal charge
- determine appropriate number of valence electrons for the atom (to balance out protons in the nucleus)
- determine how many electrons are actually around the atom
bond - contributes 1 electron
lone pair - contributes 2 electrons
describe molecular orbital theory
in molecular orbital theory, some orbitals normally around an atom no longer exist, but have instead merged to form molecular orbitals for the entire molecule.
these orbitals are filled with the 2 electrons from each pi bond
–> resulting charge around one atom is actually associated with the whole molecule
what 3 types of molecular orbitals can form from the 3 p orbitals? (draw & # nodes)
antibonding MO –highest energy –2 vertical nodes
non-bonding MO –middle energy –1 vertical node
–will not form if only 2 p orbitals contribute
bonding MO –lowest energy –no vertical nodes
what are resonance structures?
resonance structures are multiple drawings of the same compound that indicate all of its merged (partial) properties
what is a resonance hybrid?
a resonance hybrid is the actual, real molecule which is represented by the resonance structures.
it contains partial characteristics of each drawing in the resonance structure
what is delocalization of charge?
delocalization of charge is when the charge (+ or -) is spread out over the molecule
which is more stable, compounds with localized charge or compounds with delocalized charge?
delocalized charge
are molecules with resonance structures more or less stable (than an equivalent compound without resonance structures)?
more –> resonance stabilization
what is resonance stabilization?
resonance hybrids are more stable (than a similar, non-resonant compound) because the charge (+ or -) is delocalized
what 2 things must you avoid doing while drawing resonance structures?
- breaking a single bond
- exceeding an octet for second-row elements
what position are these carbon atoms in?
vinylic position
the carbon atoms participating in the double-carbon-bond
what position are these carbon atoms in?
allylic positions
the atoms directly connected to the double-bonded carbon atoms
what resonance structure pattern applies to this compound?
allylic lone pair
what resonance structure pattern applies to this compound?
allylic positive charge (allylic cation)
what resonance structure pattern applies to this compound?
lone pair adjacent to a positive charge
what resonance structure pattern applies to this compound?
a pi bond between 2 atoms of differing electronegativity
(especially C=O and C=N)
what resonance structure pattern applies to this compound?
conjugated pi bonds enclosed in a ring
what can help you determine the significance of resonance structures?
- most significant resonance structures are those in which all atoms have an octet
- more significant resonance structures have minimal charges (no more than 2 charges)
- less significant resonance structure are those in which carbon atoms bear opposite charges
what is a localized lone pair?
a localized lone pair cannot participate in resonance. it is not allylic to a pi bond, and thus stays attached to 1 atom.
an atom with a lone pair and a pi bond – which electrons participate in resonance
either, but not both
(the lone pair and the pi bond on one atom will not both participate in resonance)
