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2. Polar Covalent Bonds:
Acids and Bases
Why this chapter?
Description of basic ways chemists account for
chemical reactivity.
Establish foundation for understanding specificreactions discussed in subsequent chapters.
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2.1 Polar Covalent Bonds:
Electronegativity
Covalent bonds can have ionic character
These are polar covalent bonds
◦ Bonding electrons attracted more strongly by oneatom than by the other
◦ Electron distribution between atoms is notsymmetrical
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Bond Polarity and Electronegativity
Electronegativity (EN): intrinsic ability of an atomto attract the shared electrons in a covalent bond
Differences in EN produce bond polarity
Arbitrary scale. As shown in Figure 2.2,electronegativities are based on an arbitrary scale
F is most electronegative (EN = 4.0), Cs is least(EN = 0.7)
Metals on left side of periodic table attract electronsweakly, lower EN
Halogens and other reactive nonmetals on rightside of periodic table attract electrons strongly,higher electronegativities
EN of C = 2.5
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The Periodic Table and Electronegativity
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Bond Polarity and Inductive Effect
Nonpolar Covalent Bonds: atoms with similar EN
Polar Covalent Bonds: Difference in EN of atoms <2
Ionic Bonds: Difference in EN > 2
◦ C –H bonds, relatively nonpolar C-O, C-X bonds(more electronegative elements) are polar
Bonding electrons toward electronegative atom
◦ C acquires partial positive charge, +
◦ Electronegative atom acquires partial negativecharge, -
Inductive effect: shifting of electrons in a bond inresponse to EN of nearby atoms
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CO O
Polarity, Shape
3.5 3.52.5
O=C=O
+ --
Polar Covalent Bonds
Linear Shape (180o)
Electronegativity
Difference
< 0.5
Nonpolar
0.5
-
1.7
Polar
>
1.8
Ionic
Nonpolar Compound
CO2
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CH H
O
Polarity, Shape
O=C=O+ --
e-’s in 2 directions = 180
o
Linear
e-’s in 3 directions = 120o
+
-
Trigonal planar
Nonpolar Compound
Polar Compound
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F
F B
Polarity, Shape
4.0
4.0
2.0 +
- -
Polar Covalent Bonds
(120o)Trigonal Planar
Nonpolar Compound
BF3
F 4.0F
B
F
F-
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Polarity, Shape
CH H
H
Cl
CH H
H
ClH
CH
ClH
OH H
H-O-H
O
H
H
+
+-
+-
e-’s in 4 directions = 109.5o
Tetrahedral
Bent
4 directions = 109.5o
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Polarity, Shape
NH H
H +
-
e-’s in 4 directions = 109.5o
Pyramidal
NH H
H
NH
H+
+
(109.5o)Tetrahedral Configuration of Electrons
Trigonal Pyramid Configuration of Atoms
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Tetrahedral electron-pair
Geometries
Tetrahedral
PyramidalBent
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Electrostatic Potential Maps
Electrostatic potentialmaps show calculated
charge distributions
Colors indicate electron-
rich (red) and electron-
poor (blue) regions
Arrows indicate
direction of bondpolarity
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2.2 Polar Covalent Bonds: Dipole Moments Molecules as a whole are often polar from vector summation of
individual bond polarities and lone-pair contributions
Strongly polar substances soluble in polar solvents like water;nonpolar substances are insoluble in water.
Dipole moment () - Net molecular polarity, due to difference insummed charges
◦ - magnitude of charge Q at end of molecular dipole timesdistance r between charges = Q r, in debyes (D), 1 D = 3.336 1030 coulomb meter
length of an average covalent bond, the dipole moment would be 1.60 1029 Cm, or 4.80 D.
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Dipole Moments in Water and Ammonia
Large dipole moments
◦ EN of O and N > H
◦ Both O and N have lone-pair electrons oriented awayfrom all nuclei
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Absence of Dipole Moments
In symmetrical molecules, the dipole moments of
each bond has one in the opposite direction
The effects of the local dipoles cancel each other
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Which of the above molecules is the most
polar?
1. A
2. B
3. C4. D
5. It cannot be
determined
F
H
H
F
F
H
F
H
H
H
F
F
F
F
F
F
A B C D
Learning Check:
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Which of the above molecules is the most
polar?
1. A
2. B
3. C4. D
5. It cannot be
determined
F
H
H
F
F
H
F
H
H
H
F
F
F
F
F
F
A B C D
Solution:
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Learning Check:
21
Which of the following molecules isnonpolar?
1.H2O
2. CH3CN
3. CHCl3
4. CH2Cl25. CO2
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Solution:
22
Which of the following molecules isnonpolar?
1.H2O
2. CH3CN
3. CHCl3
4. CH2Cl25. CO2
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Which of the above molecules has (have) a
dipole moment?
1. A only
2.B only
3. C only
4. A and B
5. B and C
F
F
H
H
C
F
H
H
F
C C
F
H
A B C
H
F
Learning Check:
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Which of the above molecules has (have) a
dipole moment?
1. A only
2.B only
3. C only
4. A and B
5. B and C
F
F
H
H
C
F
H
H
F
C C
F
H
A B C
H
F
Solution:
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2.3 Formal Charges Sometimes it is necessary to have structures with formal charges
on individual atoms We compare the bonding of the atom in the molecule to the
valence electron structure
If the atom has one more electron in the molecule, it is shownwith a ―-‖ charge
If the atom has one less electron, it is shown with a ―+‖ charge
Neutral molecules with both a ―+‖ and a ―-‖ are dipolar
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• Atomic sulfur has 6
valence electrons.
Dimethyl suloxide
sulfur has only 5.
• It has lost an electron
and has positive
charge.
• Oxygen atom in
DMSO has gained
electron and has (-)
charge.
Formal Charge for Dimethyl Sulfoxide
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What are the hybridization and a formalcharge, respectively, on boron in BH4
–?
1. sp3, 02. sp3, –1
3. sp3, +1
4. sp2, –1
5. sp2, +1
Learning Check:
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What are the hybridization and a formalcharge, respectively, on boron in BH4
–?
1. sp3, 02. sp3, –1
3. sp3, +1
4. sp2, –1
5. sp2, +1
Solution:
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2.4 Resonance Some molecules are have structures that cannot be shown with
a single representation In these cases we draw structures that contribute to the final
structure but which differ in the position of the bond(s) or lonepair(s)
Such a structure is delocalized and is represented byresonance forms
The resonance forms are connected by a double-headed arrow
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Resonance Hybrids A structure with resonance forms does not alternate between
the forms Instead, it is a hybrid of the two resonance forms, so the
structure is called a resonance hybrid
For example, benzene (C6H6) has two resonance forms withalternating double and single bonds
◦
In the resonance hybrid, the actual structure, all its C-Cbonds are equivalent, midway between double and single
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2.5 Rules for Resonance Forms
Individual resonance forms are imaginary - thereal structure is a hybrid (only by knowing the
contributors can you visualize the actual structure)
Resonance forms differ only in the placement of
their or nonbonding electrons Different resonance forms of a substance don’t
have to be equivalent
Resonance forms must be valid Lewis structures:
the octet rule applies The resonance hybrid is more stable than any
individual resonance form would be
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Curved Arrows and Resonance Forms We can imagine that electrons move in pairs to
convert from one resonance form to another A curved arrow shows that a pair of electrons moves
from the atom or bond at the tail of the arrow to theatom or bond at the head of the arrow
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2.6 Drawing Resonance Forms
Any three-atom grouping with a multiple
bond has two resonance forms
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Different Atoms in Resonance Forms Sometimes resonance forms involve different atom types as
well as locations The resulting resonance hybrid has properties associated with
both types of contributors
The types may contribute unequally
The ―enolate‖ derived from acetone is a good illustration, withdelocalization between carbon and oxygen
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2,4-Pentanedione
The anion derived from 2,4-pentanedione◦ Lone pair of electrons and a formal
negative charge on the central carbon
atom, next to a C=O bond on the left and onthe right
◦ Three resonance structures result
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Which of the following statements is falseconcerning resonance structures?
1. The arrangement of nuclei in all contributing structures
must be the same.2. The arrangement of electrons in each contributing
structure is different.
3. Each atom in a contributing structure must have a
completed valence shell.4. The contributing structures may have different
energies.
5. All contributing structures must have the correct
number of valence electrons.
Learning Check:
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Which of the following statements is falseconcerning resonance structures?
1. The arrangement of nuclei in all contributing structures
must be the same.2. The arrangement of electrons in each contributing
structure is different.
3. Each atom in a contributing structure must have a
completed valence shell.4. The contributing structures may have different
energies.
5. All contributing structures must have the correct
number of valence electrons.
Solution:
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Consider all equivalent resonance structures for thecarbonate anion shown below. If the bond order is defined as
the number of electron pairs shared between two atoms,
what is the average bond order for the C-O1 bond?
1. 2
2. 3/2
3. 4/3
4. 1
5. 1/4
O
O O
1
Learning Check:
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Consider all equivalent resonance structures for thecarbonate anion shown below. If the bond order is defined as
the number of electron pairs shared between two atoms,
what is the average bond order for the C-O1 bond?
1. 2
2. 3/2
3. 4/3
4. 1
5. 1/4
O
O O
1
Solution:
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Consider all equivalent resonance structures for carbonate anion shown below. What is the
formal charge on O1?
1. –1
2. –2/3
3. –1/2
4. –1/3
5. 0
O
O O
1
Learning Check:
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Consider all equivalent resonance structures for carbonate anion shown below. What is the
formal charge on O1?
1. –1
2. –2/3
3. –1/2
4. –1/3
5. 0
O
O O
1
Solution:
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Anions with the negative charge residing on carbonsare called carbanions. In the methyl anion the carbon
is sp3 hybridized. What is the hybridization of carbon
1 in the allyl anion?
H
H
H H
H
allyl anion (a carbanion)1
1. sp3
2. sp2
3. sp
4. sp3d
5. carbon 1 is not hybridized
Learning Check:
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Anions with the negative charge residing on carbonsare called carbanions. In the methyl anion the carbon
is sp3 hybridized. What is the hybridization of carbon
1 in the allyl anion?
H
H
H H
H
allyl anion (a carbanion)1
1. sp3
2. sp2
3. sp
4. sp3d
5. carbon 1 is not hybridized
Solution:
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How many uncharged resonance
structures exist for the following
molecule?
1. Only the one shown above
2. 2
3. 3
4. 4
5. 5
Learning Check:
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How many uncharged resonance
structures exist for the following
molecule?
1. Only the one shown above
2. 2
3. 3
4. 4
5. 5
Solution:
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2.7 Acids and Bases: The Brønsted –
Lowry Definition
The terms ―acid‖ and ―base‖ can have different
meanings in different contexts
For that reason, we specify the usage with more
complete terminology
The idea that acids are solutions containing a lot of
―H+‖ and bases are solutions containing a lot of ―OH-‖
is not very useful in organic chemistry
Instead, Brønsted –Lowry theory defines acids and
bases by their role in reactions that transfer protons(H+) between donors and acceptors
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Bronsted-Lowry theory
Acid=a Proton donor
donates a proton, H+, to solvent
Example: HCl
HCl + H2O H3O+ + Cl-
hydronium ion
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Example: HNO3
HNO3 is the acid: it donates the proton.
Bronsted-Lowry theory
HNO3 + H2O H3O+ + NO3
-
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Base = a proton acceptor accepts a Proton, H+, from solvent
NH3
+ H2O NH
4
+ + OH-
Accepted H+
Bronsted-Lowry theory
NH3 is the Base: it takes the proton.
Hydroxide ions (OH-) form when water
donates the proton.
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Common Acids Battery Acid
Stomach Acid
Coca Cola
Carbonated Water
Vinegar
Citrus fruits
Vitamin C
Grapes
Aspirin
H2SO
4HCl
H3PO4
H2CO3
HC2H3O2
H3C6O7H8
HC6O6H7 H2C4O6H4
H2C9O4H8
Sulfuric AcidHydrochloric Acid
Phosphoric Acid
Carbonic Acid
Acetic Acid
Citric Acid
Ascorbic Acid Tartaric Acid
Acetyl Salicylic Acid
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Naming Acids
•Binary Acids = (-ide ending)
HCl
Hydro- ______-ic Acid
= Hydrochlor ic Acid
•Oxoacids = H, Nonmetal & O -ate ending (The higher number of O’s)
= Hydrogen Chlor ide
______________-ic Acid
HNO3
= Hydrogen Nitr ate = Nitr ic Acid
-ite ending (The lower number of O’s)
______________-ous Acid
HNO2 = Hydrogen Nitr ite = Nitr ous Acid
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Naming AcidsNon-Acid name Acid Name
H2SO4
H2SO3
H2S
H3PO4
HBr
H2CO3
HNO2 HNO3
Dihydrogen Sulf ate
Hydrogen Bromide
Trihydrogen Phosphate
Dihydrogen carbonate
Acetic Acid
Sulfur ic Acid
Hydrobromic Acid
Phosphor ic Acid
Dihydrogen Sulf ite
Dihydrogen Sulf ide
Sulfur ous Acid
Hydrosulfur ic Acid
Hydrogen Nitr ate
Hydrogen Nitr ite Nitr ous Acid
Nitr ic Acid
Hydrogen AcetateHC2H3O2
Carbonic Acid
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Naming AcidsNon-Acid name Acid Name
H2SO4
H2SO3
H2SO2
HCl
HClO
HClO2 HClO3
Dihydrogen Sulf ate
Hydrogen Chlor ide
Hydrogen hypochlor ite
Per chlor ic Acid
Sulfur ic Acid
Hydrochlor ic Acid
Dihydrogen Sulf ite
Dihydrogen Sulf ide
Sulfur ous Acid
Hyposulfur ous Acid
Hydrogen chlor ate
Hydrogen chlor ite Chlor ous Acid
Chlor ic Acid
Hydrogen Per chlor ateHClO4
Hypochlor ous Acid
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H2SO
4HCl
H3PO4
H2CO3
HC2H3O2
H3C6O7H8
HC6O6H7 H2C4O6H4
H2C9O4H8
Common AcidsBattery AcidStomach Acid
Coca Cola
Carbonated Water
Vinegar
Citrus fruitsVitamin C
Grapes
Aspirin
Strong•100% ionization•Strong electrolyte
Weak•Partial ionization
•Weak electrolyte
•Taste sour
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AcidsH-Cl + H-O-H + Cl-
HO
H
H
+
HO
H
H
+Cl-
H-Cl
H+
HC2H3O2
C2H3O21-
HC2H3O2
H-C2H3O2 + H-O-HH
OH
H
+ + C2H3O2-
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Base = gives hydroxide ions in water.(Arrhenius definition)
= takes hydrogen ions in water.(Bronsted-Lowry definition)
Bases
NaOH
Na+ + OH-OH-
OH-
Na+
Na+
NaOH
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Brønsted Acids and Bases
―Brønsted-Lowry‖ is usuallyshortened to ―Brønsted‖
A Brønsted acid is a substance that
donates a hydrogen ion (H+
) A Brønsted base is a substance that
accepts the H+
◦
―proton‖ is a synonym for H+
- loss of anelectron from H leaving the bare
nucleus—a proton
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The Reaction of Acid with Base Hydronium ion, product when base H2O gains a proton
HCl donates a proton to water molecule, yielding hydronium ion
(H3O+) [conjugate acid] and Cl [conjugate base]
The reverse is also a Brønsted acid –base reaction of the
conjugate acid and conjugate base
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2.8 Acid and Base Strength
The equilibrium constant (K eq ) for the reaction of anacid (HA) with water to form hydronium ion and theconjugate base (A-) is a measure related to thestrength of the acid
Stronger acids have larger K eq
Note that brackets [ ] indicate concentration, molesper liter, M.
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K a – the Acidity Constant
The concentration of water as a solvent does not changesignificantly when it is protonated
The molecular weight of H2O is 18 and one liter weighs 1000grams, so the concentration is ~ 55.4 M at 25°
The acidity constant, K a for HA K eq times 55.6 M (leaving[water] out of the expression)
K a ranges from 1015 for the strongest acids to very small values(10-60) for the weakest
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pK a – the Acid Strength Scale
pK a = -log K a The free energy in an equilibrium is related to –log of
K eq (DG = -RT log K eq)
A smaller value of pK a indicates a stronger acid and
is proportional to the energy difference betweenproducts and reactants
The pK a of water is 15.74
2 9 P di ti A id B R ti
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2.9 Predicting Acid –Base Reactions
from pK a Values pK
a
values are related as logarithms to equilibrium constants
Useful for predicting whether a given acid-base reaction willtake place
The difference in two pK a values is the log of the ratio of equilibrium constants, and can be used to calculate the extent of transfer
The stronger base holds the proton more tightly
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2.10 Organic Acids and Organic Bases
Organic Acids:
- characterized by the presence of positively polarized hydrogen atom
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66
Organic Acids Those that lose a proton from O –H, such as
methanol and acetic acid Those that lose a proton from C –H, usually from a
carbon atom next to a C=O double bond (O=C –C –H)
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Organic Bases Have an atom with a lone pair of electrons that can
bond to H+
Nitrogen-containing compounds derived fromammonia are the most common organic bases
Oxygen-containing compounds can react as baseswhen with a strong acid or as acids with strong bases
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68
2.11 Acids and Bases: The Lewis Definition
Lewis acids are electron pair acceptors and Lewisbases are electron pair donors
Brønsted acids are not Lewis acids because theycannot accept an electron pair directly (only a proton
would be a Lewis acid) The Lewis definition leads to a general description of
many reaction patterns but there is no scale of strengths as in the Brønsted definition of pK a
Lewis Acids and the Curved Arrow
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Lewis Acids and the Curved Arrow
Formalism
The Lewis definition of acidity includes metal cations,such as Mg2+
◦ They accept a pair of electrons when they form a bondto a base
Group 3A elements, such as BF3
and AlCl3
, are Lewisacids because they have unfilled valence orbitals and canaccept electron pairs from Lewis bases
Transition-metal compounds, such as TiCl4, FeCl3, ZnCl2,and SnCl4, are Lewis acids
Organic compounds that undergo addition reactions withLewis bases (discussed later) are called electrophiles andtherefore Lewis Acids
The combination of a Lewis acid and a Lewis base canshown with a curved arrow from base to acid
Ill stration of C r ed Arro s in Follo ing
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70
Illustration of Curved Arrows in Following
Lewis Acid-Base Reactions
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Lewis Bases Lewis bases can accept protons as well as Lewis acids,
therefore the definition encompasses that for Brønsted bases Most oxygen- and nitrogen-containing organic compounds are
Lewis bases because they have lone pairs of electrons
Some compounds can act as both acids and bases, dependingon the reaction
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All Lewis acids can also be classified
as Brønsted-Lowry acids.
1. True
2. False
Learning Check:
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All Lewis acids can also be classified
as Brønsted-Lowry acids.
1. True
2. False
Solution:
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Which statement best describes thefollowing reaction?
NH3 + BH3 H3N BH3
1. an acid-base reaction where NH3 acts as a Brønsted-Lowry acid
2. an acid-base reaction where NH3 acts as a Brønsted-
Lowry base
3. an acid-base reaction where NH3 acts as a Lewisacid
4. an acid-base reaction where NH3 acts as a Lewis
base
5. None of these adequately describes the reaction.
Learning Check:
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Which statement best describes thefollowing reaction?
NH3 + BH3 H3N BH3
1. an acid-base reaction where NH3 acts as a Brønsted-Lowry acid
2. an acid-base reaction where NH3 acts as a Brønsted-
Lowry base
3. an acid-base reaction where NH3 acts as a Lewisacid
4. an acid-base reaction where NH3 acts as a Lewis
base
5. None of these adequately describes the reaction.
Solution:
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What is the main reason why molecule A isless acidic than molecule B?
A: CH3CH2CH2-H B: CH3CH2O-H
1. There are more hydrogens in A.2. The C-H bond is weaker than the O-H bond.
3. The conjugate base of A is more stable than the
conjugate base of B.
4. In the conjugate base of B, the negative charge resideson a more electronegative atom.
5. There is resonance and inductive stabilization of
conjugate base of B.
Learning Check:
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What is the main reason why molecule A isless acidic than molecule B?
A: CH3CH2CH2-H B: CH3CH2O-H
1. There are more hydrogens in A.2. The C-H bond is weaker than the O-H bond.
3. The conjugate base of A is more stable than the
conjugate base of B.
4. In the conjugate base of B, the negative charge resideson a more electronegative atom.
5. There is resonance and inductive stabilization of
conjugate base of B.
Solution:
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Ammonia can act as all four classifications of acids or bases (Lewis acid, Lewis base,
Brønsted-Lowry acid, and Brønsted-Lowry
base.)
1. True
2. False
Learning Check:
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Ammonia can act as all four classifications of acids or bases (Lewis acid, Lewis base,
Brønsted-Lowry acid, and Brønsted-Lowry
base.)
1. True
2. False
Solution:
C
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Van der Waals interactions refer to the weak attractiveforces that occur between individual molecules and are
very important in determining the shape and properties
of biological molecules such as proteins. Which of the
following play no role in van der Waals interactions?
1. hydrogen bonding
2. dispersion forces
3. dipole-dipole forces4. magnetic forces
5. All of these are important in van der Waals
interactions.
Learning Check:
S l i
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Van der Waals interactions refer to the weak attractiveforces that occur between individual molecules and are
very important in determining the shape and properties
of biological molecules such as proteins. Which of the
following play no role in van der Waals interactions?
1. hydrogen bonding
2. dispersion forces
3. dipole-dipole forces4. magnetic forces
5. All of these are important in van der Waals
interactions.
Solution:
L i Ch k
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Which is the correct order of the pK a values?
1. H2O > HO – > H3O+
2. HO – > H3O+ > H2O
3.H3O
+
> HO
–
> H2O4. HO – > H2O > H3O
+
5. H3O+ > H2O > HO –
Learning Check:
S l ti
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Which is the correct order of the pK a values?
1. H2O > HO – > H3O+
2. HO – > H3O+ > H2O
3.H3O
+
> HO
–
> H2O4. HO – > H2O > H3O
+
5. H3O+ > H2O > HO –
Solution:
2 12 M l l M d l
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84
2.12 Molecular Models
Organic chemistry is 3-D space Molecular shape is critical in determining the
chemistry a compound undergoes in the lab, and inliving organisms
2 13 N l t I t ti
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85
2.13 Noncovalent Interactions
Several types:- Dipole-dipole forces
- Dispersion forces
- Hydrogen bonds
Di l Di l
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Dipole-Dipole
• Occur between polar molecules as a result of electrostaticinteractions among dipoles
• Forces can be attractive of repulsive depending on orientation
of the molecules
Di i F
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Dispersion Forces
• Occur between all neighboring molecules and arisebecause the electron distribution within molecules
that are constantly changing
H d B d F
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Hydrogen Bond Forces
• Most important noncovalent interaction in biological molecules
• Forces are result of attractive interaction between a hydrogen
bonded to an electronegative O or N atom and an unshared
electron pair on another O or N atom
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89
S
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90
Summary Organic molecules often have polar covalent bonds
as a result of unsymmetrical electron sharing causedby differences in the electronegativity of atoms
The polarity of a molecule is measured by its dipolemoment, .
(+) and () indicate formal charges on atoms in
molecules to keep track of valence electrons aroundan atom
Some substances must be shown as a resonancehybrid of two or more resonance forms that differ by the location of electrons.
A Brønsted( –Lowry) acid donates a proton A Brønsted( –Lowry) base accepts a proton
The strength Brønsted acid is related to the -1 timesthe logarithm of the acidity constant, pK a. Weaker acids have higher pK a’s
S ( t’d)
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91
Summary (cont’d)
A Lewis acid has an empty orbital that can acceptan electron pair
A Lewis base can donate an unshared electron pair
In condensed structures C-C and C-H are implied
Skeletal structures show bonds and not C or H (C
is shown as a junction of two lines) – other atomsare shown
Molecular models are useful for representingstructures for study
Noncovalent interactions have several types: dipole-
dipole, dispersion, and hydrogen bond forces
Learning Check:
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Which statement about the acid-base equilibrium
shown above is incorrect?
1. the equilibrium favors the products
2. water is a conjugate acid in this equilibrium
3. hydroxide is the strongest base present4. phenol is 6 times more acidic than water
5. the negative charge in the phenoxide is resonance
stabilized
OH
+ OH
O
+ H2O
pKa = 10 pKa = 16
phenol hydroxide phenoxide
Learning Check:
Solution:
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Which statement about the acid-base equilibrium
shown above is incorrect?
1. the equilibrium favors the products
2. water is a conjugate acid in this equilibrium
3. hydroxide is the strongest base present4. phenol is 6 times more acidic than water
5. the negative charge in the phenoxide is resonance
stabilized
OH
+ OH
O
+ H2O
pKa = 10 pKa = 16
phenol hydroxide phenoxide
Solution:
Learning Check:
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What is the most likely product of the following Lewis
acid-base reaction?
1. A
2. B
3. C
4. D
5. E
O
O
+ BF3 product
O
O
O
O
O
O
O
OBF3 BF3
BF3 BF3
O
O BF3
A B C D E
Learning Check:
Solution:
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What is the most likely product of the following Lewis
acid-base reaction?
1. A
2. B
3. C
4. D
5. E
O
O
+ BF3 product
O
O
O
O
O
O
O
OBF3 BF3
BF3 BF3
O
O BF3
A B C D E
Solution:
Learning Check:
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Which of these structures is not a resonance form of
the others? (The lone pairs are not shown explicitly.)
1. a
2. b
3. c
4. d
5. e
NH
NH
N
H
N N
a) b) c) d) e)
H H
Learning Check:
Solution: