CH 2020 Exam 1 Study Guide
Chapter 1 Bonding and Isomerism
- Bonding Patterns
o Hydrogen likes to form 1 bond.
o Oxygen like to form 2 bonds.
o Nitrogen likes to form 3 bonds.
o Carbon likes to form 4 bonds.
o Halogens like to form 1 bond.
- Be able to draw Lewis Dot Structures (LDS) for all types of molecules o Make sure the octet rule is followed for every atom
o Make sure the total number of valence electrons in the LDS add up to the number of electrons you calculated
o DON’T FORGET LONE PAIRS
- Formal Charge (FC)
o The charge an atom appears to have when considering that all bonding electrons ae shared equally
o To calculate formal charge, take the number of valence electrons from the periodic table and subtract the number of electrons surrounding the atom.
Resonance Structures and Multiple Bonds
- Electronegativity is an atoms willingness to adopt an electron. o It increases up and to the right
o Fluorine is the most electronegative atom
- Bond-Line Formulas (Skeletal/Polygon)
o Shows carbon Skelton
o Lines are drawn in a zigzag format so every end intersection represents a carbon
o Omit the H atoms
o Include functional groups
o REMEMBER EACH CARBON GETS 4 BONDS
- Drawing Resonance structures
o Arrows are used to show electron involvement
Move electrons toward the positive charge and away from the negative charge
Only pi electrons or lone pair electrons (not sigma electrons or atoms) may be shifted only to adjacent atoms or bond positions ∙ From pi bond to adjacent bond
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∙ From pi bond to adjacent atom
∙ From an atom (lone pair) to an adjacent bond
Resonance structures in which an atom carries more than its quota of electrons (8 for C, N, O, F) are NOT contributors to the real structure.
The more important RS (Resonance Structure) (major vs. minor) show each atom with a complete octet and as little charge
separation as possible. Don't forget about the age old question of What are our closest living relatives?
o Be able to identify and name functional groups
Acids and Bases
o Bronsted-Lowry Theory
Strong bases produce weak acids
Strong acids produce weak bases
o Strong and Weak acids and bases
Strong acids undergo complete dissociation
Weak acids undergo partial dissociation
Classified as strong or weak based on their affinity for H+
Similar to ammonia
Undergo reversible reactions
A strong acid can drive it to completion
o Carboxylic Acids
Weak acids Don't forget about the age old question of How do you illustrate vectors?
Can be driven to completion by a strong base
o pH and pKa
the lower the pKa the more acidic
o Organic Acids and Bases
∙ pKa values from 4-5
∙ pKa values from 15-19
∙ pKa values from 35-40
∙ pKa values around 10
Protonated Oxygen If you want to learn more check out What is the function of the simple columnar epithelium?
∙ pKa values around -2
o REMEMBER: when drawing arrows to show how the products of a reaction are formed, they always go from ELECTRONS TO THE H and then from the BOND TO THE ATOM
o The reaction is always favored from the Strong Acid to the Weak Acid o Acidity increases as pKa decreases
Factors Affecting Acidity (ARIO)
o Atom If you want to learn more check out What are passive leg exercises?
Size: the larger atom disperses the negative charge over a larger region
Electronegativity: the more electronegative atom can carry the negative more readily
If the conjugate base of an acid is able to move the negative charge to other atoms it is more stable, making the acid more acidic
o Inductive effect
Election withdrawing groups (EWG) can disperse the negative charge, making the compound more acidic
The closer an electronegative atom is to the negative sign the more acidic the compound
o Orbital (Hybridization)
The less electron domains the more acidic
The less p’s in the hybridization the more acidic
Acid-Base properties of amino acids
o If the pH of a solution is less than pKa, the proton is ON
o If the pH of a solution is greater than the pKa, the proton is OFF o Electrophoresis: separation of amino acids
Chapter 2 Alkanes
- Compounds with the same molecular formula and different connectivity - Longer chains have more contact with each other, which gives them a higher boiling point Don't forget about the age old question of What were some of the characteristics of paleolithic society?
Alkanes and Cycloalkanes
- Compounds with no double bonds are called saturated hydrocarbons - Compounds with double bonds are called saturated hydrocarbons - All have the –ane ending
- “cyclo” means ring
- Naming alkanes:
o Count the number of carbons on the longest chain
This gives you the pre fix you need to go with –ane
If the molecule contains a double bond it has to be counted as part of the longest chain
o Give the any remaining substituents a name based on the table below and describe their place
o Remember to separate numbers with commas and letters from numbers with a hyphen
- The longer the chain (more contact area) the higher the boiling point o The more compact a molecule is the harder it is for the molecules to connect, making it easier to break them apart, resulting in a lower boiling point
o Oxygen forms stronger H-bonds than Nitrogen
Reactions of Alkanes
- Two primary reactions
In the presence of uv light, the reactants produce a free radical Free radical mechanism
∙ Arrows must be drawn with 1 barb
∙ 3 stages:
Becomes a cycle
∙ Free radicals can do 3 things:
o Abstract H-atoms
o Add to a double bond
∙ Free Radical Stability
o Treat radicals like C+ atoms