Kaplan Organic Chemistry Chapter 3 : Bonding – Flashcards
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Atomic Orbitals
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the regions around the nucleus within which the electrons have the highest probability of being found
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Principal Quantum Number - n
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Number that corresponds to the energy level of a given electron in an atom, is essentially a measure of size The smaller the number the closer the shell is to the nucleus and thus has lower energy, Values are up to 7 on the MCAT
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Azimuthal Quantum Number - l
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Number that corresponds to the number of subshells in an each electron shell Ranges from 0 --> n-1 Energy increases as the azimuthal quantum number increases
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Magnetic Quantum Number - ml
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Number that corresponds to the orbitals within each subshell Ranges from -l to +l There are several types of orbitals each with a specific shape
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s-orbital
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An atomic orbital that is spherical and symmetrical, centered on the nucleus
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p-orbital
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An atomic orbital that is composed of two lobes located symmetrically about the nucleus and contains a node
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Node
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Area where the probability of finding an electron is zero
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d-orbital
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An atomic orbital that is composed of four symmetrical lobes and contains two nodes
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Spin quantum number - ms
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Each orbital can hold two electrons, which is distinguished by this.
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Molecular Orbitals
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Occurs when 2 atomic orbitals combine; apply to the entire molecule Obtained mathematically by adding or subtracting the wave functions of atomic orbitals
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Bonding Orbital
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Occurs when the signs of the wave functions are the same, are lower energy, more stable molecular orbital that can be occupied by two electrons of a covalent bond
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Antibonding Orbital
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Occurs when the signs of the wave functions are different, are higher energy, less stable A molecular orbital formed by the overlap of two or more atomic orbitals; energy is greater than the energy of the combining atomic orbitals
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Sigma Bond
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a bond formed when two atomic orbitals form head-to-head or tail-to-tail overlap, these atomic orbitals combine to form a molecular orbital that is symmetrical around the axis connecting the two atomic nuclei All single bonds are sigma bonds
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Pi Bond
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Bond formed when two p-orbitals line up in a parallel fashion, electron clouds overlap forming the pi-bond Cannot exist independently of a sigma bond Prevents free rotation around the bond axis A Pi-bond on top of an existing sigma bond forms a double bond 2 Pi-bonds with a sigma bond form a triple bond
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Double Bond
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Formed by a single pi bond along with a sigma bond Involves the sharing of 2 pairs of electrons between two atoms Involved in resonance resulting in more rigid structures
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Triple Bond
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Formed by 2 pi bonds along with a sigma bond Involves the sharing of 3 pairs of electrons between two atoms Shortest in length, requires the most energy to break Involved in resonance resulting in more rigid structures
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Hybridization
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Several atomic orbitals mix to form the same total number of equivalent hybrid orbitals
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Hybrid Orbitals
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An orbital that results from the mixing of different kinds of atomic orbitals
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S character
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Fraction of a hybrid orbital that corresponds to an s orbital; about one half for sp, one third for sp2 and one forth for sp3
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sp3
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Hybrid atomic orbital formed by the combination of one s atomic orbital and three p atomic orbitals. Creating 4 sp3 hybridized orbitals This hybridization is commonly seen in alkanes, or carbons with 4 substiuent groups. 25% s character, 75% p character Tetrahedral Bond angles of 109.5 degrees Example : Methane
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sp2
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Hybrid atomic orbital formed by the combination of one s atomic orbital and 2 p atomic orbitals. Creating 3 sp2 hybridized orbitals This hybridization is commonly seen in alkenes, or atoms possessing a double bond. 33% s character, 67% p character Trigonal Planar Bond angles of 120 degrees Example : Alkenes
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sp hybridization
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Hybrid atomic orbital formed by the combination of one s atomic orbital and 2 p atomic orbitals. Creating 2 sp hybridized orbitals This hybridization is commonly seen in alkynes, or atoms with triple bonds, or 2 double bonds. 50% s character, 50%p character Linear Bond angles of 180 degrees Example : Alkynes, CO2
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Resonance
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Delocalization of electrons causing partial double bond character, often seen in aromatic rings, or conjugated hydrocarbons
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Conjugation
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Alternating single and multiple bonds, delocalization of these electrons will cause shared bond characters. The electron density is shared amongst the structure If forms of resonant structures have differing stability, electron density will favor the most stable form Allows for more rigid structures
