SOLUTION MANUAL FOR
ORGANIC CHEMISTRY 7TH
EDITION BY BROWN
,1 Covalent Bonding and Shapes of Molecules Chapter 1 1
CHAPTER 1
Solutions to the Problems
Problem 1.1 Write and compare the ground-state electron configurations for each pair of elements:
(a) Carbon and silicon
C (6 electrons) 1s2 2s2 2p2
Si (14 electrons) 1s2 2s2 2p6 3s2 3p2
Both carbon and silicon have four electrons in their outermost (valence) shells.
(b) Oxygen and sulfur
O (8 electrons) 1s2 2s2 2p4
S (16 electrons) 1s2 2s2 2p6 3s2 3p4
Both oxygen and sulfur have six electrons in their outermost (valence) shells.
(c) Nitrogen and phosphorus
N (7 electrons) 1s2 2s2 2p3
P (15 electrons) 1s2 2s2 2p6 3s2 3p3
Both nitrogen and phosphorus have five electrons in their outermost (valence) shells.
Problem 1.2 Show how each chemical change leads to a stable octet.
(a) Sulfur forms S2-. (b) Magnesium forms Mg2+.
S (16 electrons): 1s2 2s2 2p6 3s2 3p4 Mg (12 electrons): 1s2 2s2 2p6 3s2
S 2- (18 electrons): 1s2 2s2 2p6 3s2 3p6 Mg2+ (10 electrons): 1s2 2s2 2p6
Problem 1.3 Judging from their relative positions in the Periodic Table, which element in each set is more electronegative?
(a) Lithium or potassium
In general, electronegativity increases from left to right across a row and from bottom to top of a column in the
Periodic Table. This is because electronegativity increases with increasing positive charge on the nucleus and with
decreasing distance of the valence electrons from the nucleus. Lithium is closer to the top of the Periodic Table and
thus more electronegative than potassium.
(b) Nitrogen or phosphorus
Nitrogen is closer to the top of the Periodic Table and thus more electronegative than phosphorus.
(c) Carbon or silicon
Carbon is closer to the top of the Periodic Table and thus more electronegative than silicon.
Problem 1.4 Classify each bond as nonpolar covalent, or polar covalent, or state that ions are formed.
(a) S-H (b) P-H (c) C-F (d) C-Cl
Recall that bonds formed from atoms with an electronegativity difference of less than 0.5 are considered nonpolar
covalent and with an electronegativity difference of 0.5 or above are considered a polar covalent bond.
Difference in
Bond electronegativity Type of bond
S-H 2.5 - 2.1 = 0.4 Nonpolar covalent
P-H 2.1 - 2.1 = 0 Nonpolar covalent
C-F 4.0 - 2.5 = 1.5 Polar covalent
C-Cl 3.0 - 2.5 = 0.5 Polar covalent
Problem 1.5 Using the symbols δ- and δ+, indicate the direction of polarity in each polar covalent bond.
(a) C-N (b) N-O
δ+ δ- δ+ δ-
C-N N-O
Nitrogen is more electronegative than carbon Oxygen is more electronegative than nitrogen
,2 Covalent Bonding and Shapes of Molecules Chapter 1 2
(c) C-Cl
δ+ δ-
C-Cl
Chlorine is more electronegative than carbon
Problem 1.6 Draw Lewis structures, showing all valence electrons, for these molecules.
(a) C2H6 (b) CS2 (c) HCN
H H
H C C H S C S H C N
H H
Problem 1.7 Draw Lewis structures for these ions, and show which atom in each bears the formal charge.
(a) CH3 NH3 + (b) CO3 2- (c) HO-
Methylammonium ion Carbonate ion Hydroxide ion
H H O
+
H C N H O C O O H
H H
Problem 1.8 Draw Lewis structures and condensed structural formulas for the four alcohols with molecular formula C4 H 1 0O.
Classify each alcohol as primary, secondary, or tertiary.
H
H O H
H H H H
H C C C H
H C C C O H H H O H
H H
H H H C C C C H H C H
H H H H H C H H
H H H H
H C C C C O H H OH
OH
H H H H
CH3 CHCH 2OH CH 3 C CH3
CH3CH2CH2CH2OH CH3CH2 CHCH3
CH3 CH3
Primary Primary Secondary Tertiary
Problem 1.9 Draw structural formulas for the three secondary amines with molecular formula C4 H 1 1N.
H H H H H H H H H H H H H H
H C C N C C H H C N C C C H H C N C C H
H H H H H H H H H H
H C H
H
Problem 1.10 Draw condensed structural formulas for the three ketones with molecular formula C5 H 1 0O.
O O O
CH3CH2CH2CCH3 CH3CHCCH 3 CH3CH2CCH2 CH3
CH3
, 3 Covalent Bonding and Shapes of Molecules Chapter 1 3
Problem 1.11 Draw condensed structural formulas for the two carboxylic acids with molecular formula C4 H 8 O 2 .
CH3 CH CO2H
CH3 CH2 CH2 CO2H
CH3
Problem 1.12 Draw structural formulas for the four esters with molecular formula C4 H 8 O 2 .
H H O H H O H H O H H
H C C C O C H H C C O C C H H C O C C H
H H H H H H H
H C H
O H H H
H
H C O C C C H
H H H
Problem 1.13 Predict all bond angles for these molecules.
(a) CH3 OH
H 109.5o
C O
H H
H
109.5o
(b) PF3
••
P
F F
F
109.5o
(c) H2 CO3 (Carbonic Acid)
120o 120o
109.5o O 109.5o
H C H
O O
120o
MCAT Practice: Questions
Fullerenes
A. The geometry of carbon in diamond is tetrahedral, while carbon’s geometry in graphite is trigonal planar. What is the
geometry of the carbons in C6 0?
1. They are all tetrahedral.
2. They are all trigonal planar.
3. They are all pyramidal with bond angles near 109.5°.
4. They are not perfectly trigonal planar but have an extent of pyramidalization. The curve of the
buckyball surface is curved requiring some extent of pyramidilization.
ORGANIC CHEMISTRY 7TH
EDITION BY BROWN
,1 Covalent Bonding and Shapes of Molecules Chapter 1 1
CHAPTER 1
Solutions to the Problems
Problem 1.1 Write and compare the ground-state electron configurations for each pair of elements:
(a) Carbon and silicon
C (6 electrons) 1s2 2s2 2p2
Si (14 electrons) 1s2 2s2 2p6 3s2 3p2
Both carbon and silicon have four electrons in their outermost (valence) shells.
(b) Oxygen and sulfur
O (8 electrons) 1s2 2s2 2p4
S (16 electrons) 1s2 2s2 2p6 3s2 3p4
Both oxygen and sulfur have six electrons in their outermost (valence) shells.
(c) Nitrogen and phosphorus
N (7 electrons) 1s2 2s2 2p3
P (15 electrons) 1s2 2s2 2p6 3s2 3p3
Both nitrogen and phosphorus have five electrons in their outermost (valence) shells.
Problem 1.2 Show how each chemical change leads to a stable octet.
(a) Sulfur forms S2-. (b) Magnesium forms Mg2+.
S (16 electrons): 1s2 2s2 2p6 3s2 3p4 Mg (12 electrons): 1s2 2s2 2p6 3s2
S 2- (18 electrons): 1s2 2s2 2p6 3s2 3p6 Mg2+ (10 electrons): 1s2 2s2 2p6
Problem 1.3 Judging from their relative positions in the Periodic Table, which element in each set is more electronegative?
(a) Lithium or potassium
In general, electronegativity increases from left to right across a row and from bottom to top of a column in the
Periodic Table. This is because electronegativity increases with increasing positive charge on the nucleus and with
decreasing distance of the valence electrons from the nucleus. Lithium is closer to the top of the Periodic Table and
thus more electronegative than potassium.
(b) Nitrogen or phosphorus
Nitrogen is closer to the top of the Periodic Table and thus more electronegative than phosphorus.
(c) Carbon or silicon
Carbon is closer to the top of the Periodic Table and thus more electronegative than silicon.
Problem 1.4 Classify each bond as nonpolar covalent, or polar covalent, or state that ions are formed.
(a) S-H (b) P-H (c) C-F (d) C-Cl
Recall that bonds formed from atoms with an electronegativity difference of less than 0.5 are considered nonpolar
covalent and with an electronegativity difference of 0.5 or above are considered a polar covalent bond.
Difference in
Bond electronegativity Type of bond
S-H 2.5 - 2.1 = 0.4 Nonpolar covalent
P-H 2.1 - 2.1 = 0 Nonpolar covalent
C-F 4.0 - 2.5 = 1.5 Polar covalent
C-Cl 3.0 - 2.5 = 0.5 Polar covalent
Problem 1.5 Using the symbols δ- and δ+, indicate the direction of polarity in each polar covalent bond.
(a) C-N (b) N-O
δ+ δ- δ+ δ-
C-N N-O
Nitrogen is more electronegative than carbon Oxygen is more electronegative than nitrogen
,2 Covalent Bonding and Shapes of Molecules Chapter 1 2
(c) C-Cl
δ+ δ-
C-Cl
Chlorine is more electronegative than carbon
Problem 1.6 Draw Lewis structures, showing all valence electrons, for these molecules.
(a) C2H6 (b) CS2 (c) HCN
H H
H C C H S C S H C N
H H
Problem 1.7 Draw Lewis structures for these ions, and show which atom in each bears the formal charge.
(a) CH3 NH3 + (b) CO3 2- (c) HO-
Methylammonium ion Carbonate ion Hydroxide ion
H H O
+
H C N H O C O O H
H H
Problem 1.8 Draw Lewis structures and condensed structural formulas for the four alcohols with molecular formula C4 H 1 0O.
Classify each alcohol as primary, secondary, or tertiary.
H
H O H
H H H H
H C C C H
H C C C O H H H O H
H H
H H H C C C C H H C H
H H H H H C H H
H H H H
H C C C C O H H OH
OH
H H H H
CH3 CHCH 2OH CH 3 C CH3
CH3CH2CH2CH2OH CH3CH2 CHCH3
CH3 CH3
Primary Primary Secondary Tertiary
Problem 1.9 Draw structural formulas for the three secondary amines with molecular formula C4 H 1 1N.
H H H H H H H H H H H H H H
H C C N C C H H C N C C C H H C N C C H
H H H H H H H H H H
H C H
H
Problem 1.10 Draw condensed structural formulas for the three ketones with molecular formula C5 H 1 0O.
O O O
CH3CH2CH2CCH3 CH3CHCCH 3 CH3CH2CCH2 CH3
CH3
, 3 Covalent Bonding and Shapes of Molecules Chapter 1 3
Problem 1.11 Draw condensed structural formulas for the two carboxylic acids with molecular formula C4 H 8 O 2 .
CH3 CH CO2H
CH3 CH2 CH2 CO2H
CH3
Problem 1.12 Draw structural formulas for the four esters with molecular formula C4 H 8 O 2 .
H H O H H O H H O H H
H C C C O C H H C C O C C H H C O C C H
H H H H H H H
H C H
O H H H
H
H C O C C C H
H H H
Problem 1.13 Predict all bond angles for these molecules.
(a) CH3 OH
H 109.5o
C O
H H
H
109.5o
(b) PF3
••
P
F F
F
109.5o
(c) H2 CO3 (Carbonic Acid)
120o 120o
109.5o O 109.5o
H C H
O O
120o
MCAT Practice: Questions
Fullerenes
A. The geometry of carbon in diamond is tetrahedral, while carbon’s geometry in graphite is trigonal planar. What is the
geometry of the carbons in C6 0?
1. They are all tetrahedral.
2. They are all trigonal planar.
3. They are all pyramidal with bond angles near 109.5°.
4. They are not perfectly trigonal planar but have an extent of pyramidalization. The curve of the
buckyball surface is curved requiring some extent of pyramidilization.
