Organic Chemistry Bonding Flashcards
There are two types of chemical ___: ionic, in which an electron is transferred from one atom to another, and covalent, in which pairs of electrons are shared between two atoms
bonds
The first three quantum numbers, n, l, and m, describe the size, shape, and number of the ___ an element possesses. The quantum number n corresponds to the energy levels in an atom and is essentially a measure of size. Within each electron shell, there can be several types of orbitals (s, p, d, and f, corresponding to the quantum numbers l = 0, 1, 2, 3, and 4). Each type of atomic orbital has a specific shape. An s orbital is spherical and symmetrical, centered around the nucleus. A p orbital is composed of two lobes located symmetrically about the nucleus and contains a node (an area where the probability of finding an electron is zero). A d orbital is composed of four symmetrical lobes and contains two nodes. Both d and f orbitals are complex in shape and are rarely encountered in organic chemistry.
atomic orbitals
Two atomic orbitals can be combined to form a ___ (MO). Molecular orbitals are obtained mathematically by adding the wave functions of the atomic orbitals. If the signs of the wave functions are the same, a lower-energy bonding orbital is produced. If the signs are different, a higher energy antibonding orbital is produced
molecular orbital
When a molecular orbital is formed by head-to-head overlap, the resulting bond is called a ___. All single bonds are sigma bonds and contain two electrons. Shorter single bonds are stronger than longer single bonds
sigma bond
When two p orbitals overlap in a parallel fashion, a bonding MO is formed, called a pi bond. When both a sigma and a pi bond exist between two atoms, a ___ is formed. When a sigma bond and two pi bonds exist, a triple bond is formed
double bond
A ___ cannot exist independently of a sigma bond. The formation of the sigma bond between two atoms orients their p orbitals to overlap from side to side, allowing the pi bond to form. In general, pi bonds are weaker than sigma bonds. It is possible to break the pi bond of a double bond but leave the sigma bond intact; however, the sigma bond cannot be broken unless the pi bond is broken first
pi bond
___ are formed by mixing different types of atomic orbitals. If one s orbital and three p orbitals are mathematically combined, the result is four identical sp3 hybrid orbitals that have a new shape. These four orbitals will point toward the vertices of a tetrahedron, minimizing repulsion. This explains the preferred tetrahedral geometry adopted by carbon when it has four single bonds to other atoms
hybrid orbitals
The ___ is accomplished by promoting one of the 2s electrons into the 2pz orbital. This produces four valence orbitals, each with one electron, which can be mathematically mixed to create the hybrids. These four hybridized orbitals explain the four symmetrical CH found in methane
hybridization
Although carbon is often found bonded to four other atoms with sp3 ___, there are other possibilities,. If one s orbital and two p orbitals are mixed, three identical sp2 hybrid orbitals are obtained.
In ethylene, the third p orbital of each carbon atom is left unhybridized and participates in the pi bond. The three sp2 orbitals are 120 degrees apart, allowing maximum separation. These orbitals participate in the formation of the C double bonded to C and C single bonded to H bonds
hybridization
If two p orbitals are used to form the pi bonds of a triple bond and the remaining p orbital is mixed with an s orbital, two identical sp hybrid orbitals are obtained. The remaining two p orbitals of each carbon atom are left unhybridized and participate in creating two pi bonds, resulting in a triple bond. The two sp ___ are oriented 180 degrees apart, explaining the linear structure of molecules such as acetylene
hybrid orbitals
Single bond Sigma sp3 109.5 C-C, C-H Double bond sigma pi sp2 120 C || C; C||O \_\_\_ sigma pi pi sp 180 C|||C; C|||N
triple bond
