OChem Unit 1
determining unsaturation number/degree of unsaturation
(2C + 2 + N - H - X)/2 Ignore Oxygen, X is F/Cl/Br/I tells you how many rings and multiple bonds are present if 0, molecule is saturated
cation
+ charge, more protons than electrons
anion
- charge, more electrons than protons
What is the formal charge of carbon in carbon monoxide (CO) when drawn with a triple bond?
-1
What is the formal charge of the carbon in carbon dioxide (CO2) when drawn with two double bonds?
0
instructions for lewis dot structure
1) calculate the number of valence electrons in a molecule (add ve's of each element) 2) calculate the number of electrons required for an octet 3) subtract valence electrons from electrons needed and divide by two for total number of bonds
How many electrons are around phosphorus in phosphoric acid (H3PO4)?
10
What is the approximate value of the H-C-H bond angle in methane, CH4?
109.5
What is the ground-state electronic configuration of a fluorine atom?
1s2, 2s2, 2p5
What is the ground-state electronic configuration of a magnesium cation (Mg2+)?
1s2, 2s2, 2p6
What is the ground-state electronic configuration of a chlorine anion (Cl—)?
1s2, 2s2, 2p6, 3s2, 3p6
How many constitutional isomers are there for C3H6?
2
How many constitutional isomers are there for a molecule having the molecular formula C2H6O?
2
How many different isomers are there for a compound having the molecular formula C3H6O?
7
Which of the following statements explain why HBr is a stronger acid than HF?
Br- is more stable than F- because Br- is larger than F-.
Which of these compounds is the strongest acid: CH3OH, CH3NH2, BrCH2OH, or CH3Cl
BrCH2OH
Rank the following compounds in order of increasing acidity, putting the least acidic first. CH3COOH, FCH2COOH, ClCH2COOH, and BrCH2COOH
CH3COOH < BrCH2COOH < ClCH2COOH < FCH2COOH
Which of the following species is the conjugate base of methanol, CH3OH?
CH3O-
Which of the following compounds is both a Bronsted-Lowry acid and base? Options: CH3OH, CH3COCH3, H2O, (CH3)3N
CH3OH and H2O
Which of the following statements correctly describes the typical number of bonds for carbon, nitrogen, and oxygen in most neutral organic molecules?
Carbon forms 4 covalent bonds, nitrogen forms 3 covalent bonds, and oxygen forms 2 covalent bonds.
Which of the following statements about constitutional isomers is true?
Constitutional isomers are different molecules having the same molecular formula.
Which of the following compounds has an atom with more than eight valence electrons?
H2SO4
Which is the correct Lewis structure for acetic acid (CH3CO2H)?
IV
Which of the following statements about bonding is true?
Ionic bonds result from the transfer of electrons from a metal to a non-metal.
Which of the following statements about Lewis acids is true?
Lewis acids are electron pair acceptors.
Which of the following statements about Lewis bases is true?
Lewis bases are electron pair donors.
Better resonance structure or major contributor
More bonds, fewer charges Formal charges closer to 0 are better Negative charges are more electronegative and favored Same sign on adjacent atoms will not be favored The most electronegative atom will prefer to take the negative charge
Which of the following would most likely form an ionic bond? C-C, C-N, C-O, Na-O?
Na-O
Which of the following would you expect to have ionic bonds?
NaCl
Which of the following statements about resonance structures is not true?
Resonance structures are in equilibrium with each other.
Which of the following statements about resonance structures is true?
Resonance structures have the same placement of atoms but different arrangement of electrons
What 2 things will change between two resonance structures?
The position of multiple bonds and non-bonded electrons.
Which of the following statements about acid strength is true?
The stronger the acid, the smaller the pKa.
Which of the following statements about valence electrons is true?
They are the outermost electrons.
Drawing Resonance Structures
They differ in the position of multiple bonds and nonbonded electrons. Placement of atoms and single bonds stays the same. Resonance structures need the same number of unpaired electrons.
VSEPR theory
Valence-shell electron-pair repulsion theory; because electron pairs repel, molecules adjust their shapes so that valence electron pairs are as far apart as possible 2 groups = linear = 180 degree angle 3 groups = trigonal planar = 120 degree angle 4 groups = tetrahedral = 109.5 degree angle
resonance stabilized
a molecule or ion that has two or more resonance structures
The more stable the conjugate base the _______________ the acid.
acidic
isotopes
atoms with different neutron numbers, so atomic weights are different
resonance hybrid
composite of all possible resonance structures
modern definition of organic compounds
compounds having at least carbon and hydrogen, carbon and carbon covalent bonds
Bond length ____ across a row of the periodic table as the size of the atom decreases
decreases
Bond length __ down a column as sizes increases
increases
electronegativity
measure of an atoms attraction for electrons in a bond or to form a molecule or compounds; positively charged ions are usually more electronegative than negatively charged ions
atomic number
number of protons in nucleus (which is also equal to electrons), on bottom
formal charge
number of valence electrons - number of bonds - number of nonbonding electrons
resonance structure
one of the two or more equally valid electron dot structures of a molecule or polyatomic ion resonance structures are not in equilibrium with each other, there is no movement of electrons between them resonance structures are not isomers because they only differ in the arrangement of electrons
BL bases
proton acceptors
BL acids
proton donors
covalent bond
sharing of electrons between two nuclei (usually nonmetal to nonmetal)
mass number
sum of protons and neutrons, on top
What is the molecular geometry around the Carbon atom in CH4?
tetrahedral
atomic weight
total average mass of all existing isotopes of the element, measured in amu (g/mol of atoms)
What is the molecular geometry around Boron in the molecule BH3?
trigonal planar
