CHEM266 Study Guide - Final Guide: Neopentane, Boiling Point, Group 2 Organometallic Chemistry
7 May 2018
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Organic Chemistry: Section 1 - 14
Alkanes
n-Alkanes are the simplest organic compounds. When drawing alkane structures, hydrogens
bonded to carbon are not drawn, but hydrogens bonded to heteroatoms (atoms other than
carbon, such as oxygen, or nitrogen) must be drawn. Some key things to remember when
naming:
✴The prefixes “iso-“ and “neopentyl-“ are included in the alphabetization.
✴The prefixes “sec” and “tert” are not included in the alphabetization.
✴When two chains of equal length competes to be parent, chose the chain with the
greatest number of substituents.
✴When branching first occurs at an equal distance from either end of the parent chain,
chose the name that gives the lowest sum of substituent locations.
✴Halogens (F, Cl, Br, I, NO2, phenyl) drop the “ine” suffix and gain and “o” suffix.
Functional Groups
Priority
Carboxylic acids > esters > amides > nitrile > aldehydes > ketones > alcohols > amines >
alkenes, alkynes > ether, phenyl, halo, nitro
Alkenes and Alkynes
✴ Alkenes are double bonds that contain one sigma and one pi bond; there is no
rotation about the double bond
✴The suffix is “ene”
✴Alkynes are triple bonds that contain one sigma and two pi bonds the carbons are
linear sp hybridized
✴The suffix is “yne”
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Classification of Carbons
The number of molecules attached to a carbon classifies what type of carbon it is. This is
important for future reference in determining functional properties. In addition, hydrogens get
their classification from the carbon that they are bonded to, for instance: the hydrogens on a
primary carbon are also classified as primary. The same is also true for alcohols and amines.
✴Primary Carbons: an sp3 carbon bonded to one other carbon.
✴Secondary Carbon: an sp3 carbon bonded to two other carbons.
✴Tertiary Carbon: an sp3 carbon bonded to three other carbons.
✴Quaternary Carbon: an sp3 carbon bonded to four other carbons.
Electronegativity
Measure of the tendency for an atom in a molecule to attract a pair of electrons.
Electronegativity increases towards Fluorine (to the right and up) on the periodic table.
✴Non polar covalent bonds: 0.0 - 0.4
✴Polar covalent bonds: 0.5 - 1.6
✴Ionic bonds: anything 1.7 or greater.
✴When drawing an ionic bond between two atoms, do NOT draw a line connecting
them; there is NO sigma bond, it is simply a transfer of electrons instead of sharing.
Formal Charge
Created from the imbalance of electrons and protons on an atom. If there are formal charges
on atoms within a molecule, but the sum of these formal charges is zero, the molecule is still
considered to be overall neutral.
Calculating the formal charge on an atom in a given molecule
1. Refer to the periodic table to identify how many valence electrons that atom have
(each group from I - skips 2-12 - to VIIA increases by one in the number of valence
electrons, starting with one in group I).
2. Count the number bonds made with other atom; a double counts as two, and a triple
bond counts as three. In simple terms, count the number of “sticks”.
3. Count the number of electrons (dots); meaning lone pair or radical electrons.
4. Formal charge = valence electrons in that atom - “sticks” - “dots”
Drawing appropriate charges on a molecule
1. Add up the total number of valence electrons.
2. Determine the number of electrons needed for a full octet
3. Subtract 1 from 2 then divide the difference by two; this is how many bonds are
involved in the molecule
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Valence Shell Electron Repulsion Theory (VSERP)
Helps predict the spatial arrangement of atoms in polyatomic molecules or ions. Theory states
that electron pairs arrange themselves so as to achieve maximal distance from each other.
Atomic geometry considers only bonds whereas the arrangement of electron pairs considers
both bonds and lone pairs of electrons.
Steric Number
The steric number corresponds to the hybridization of the atom. The steric number is the SUM
of SIGMA bonds and LONE PAIRS (e.g., 2 electrons = 1 pair). Recall that a double bond contains
one sigma and one pi bond, a triple bond contains one sigma and TWO pi bonds. The number of
sigma bonds does not increase!
✴2 = sp = linear
✴3 = sp2 = trigonal planar
✴4 = sp3 = tetrahedral
When an orbital is hybridized (e.g., sp#) it signifies energetically equivalent bonds. Combining
the one 2s orbital with the 3 2p orbitals gives you 4 hybridized orbitals that can have 8
electrons.
Principles and Rules
✴The Aufbau Principle: always fill the lowest energy orbitals first.
✴The Pauli Exclusion Principle: each orbital can only contain up to two electrons at a
time, and these electrons have opposite spin.
✴Hund’s rule: when dealing with orbitals with the same energy level (e.g., three 2p
orbitals) each orbital receives one electron first before they are paired up.
Resonance Structures
Shows us how electrons move in a pi bond. If a molecule contains resonance, the negative (or
positive) charge can delocalize, thus making the molecule more stable. The energy of the
actual molecule as a whole is lower than the energy of any single contributing molecule. You
cannot be asked the hybridization of molecules with lone pairs if they resonant.
Name
Bond angle
Steric Number
Hybridization
Linear (electronic)
Tetrahedral
109.5
4
sp3
180 degrees
Trigonal planar
107
3
sp2
Triple bond involved
Bent
105
2
sp
Triple bond involved
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find more resources at oneclass.com
Document Summary
When drawing alkane structures, hydrogens bonded to carbon are not drawn, but hydrogens bonded to heteroatoms (atoms other than carbon, such as oxygen, or nitrogen) must be drawn. The pre xes iso- and neopentyl- are included in the alphabetization. The pre xes sec and tert are not included in the alphabetization. When two chains of equal length competes to be parent, chose the chain with the greatest number of substituents. When branching rst occurs at an equal distance from either end of the parent chain, chose the name that gives the lowest sum of substituent locations. Halogens (f, cl, br, i, no2, phenyl) drop the ine suf x and gain and o suf x. Carboxylic acids > esters > amides > nitrile > aldehydes > ketones > alcohols > amines > alkenes, alkynes > ether, phenyl, halo, nitro. Alkenes are double bonds that contain one sigma and one pi bond; there is no rotation about the double bond.
