STUDY GUIDE AND - Third Edition Joel Karty Joel Karty Taylor Mach...

STUDY GUIDE AND

SOLUTIONS MANUAL

Organic Chemistry: Principles and Mechanisms

Third Edition Joel Karty Joel Karty Taylor Mach Marie M. Melzer 1 / 4

CHAPTER 1 | Atomic and Molecular Structure Your Turn Exercises Your Turn 1.1 Think When designating orbitals as 1 s , 2 s , 2 p , and so on, what corresponds to the shell number? Which orbitals share that designation? Which electrons are in this shell?Solve The number appearing before the s and p designation specifies the shell number. The 2 s and 2 p orbitals are in the second shell, noted by the dashed box. Electrons (3)–(10) are in the second shell. The 3 s and 3 p orbitals are in the third shell, noted by the dashed circle. Electrons (11)–(18) are in the third shell.Your Turn 1.2 Think 2 / 4

How many total electrons does carbon have? What is the electron configuration for carbon? What distinguishes valence electrons from core electrons?Solve The valence electrons are in the highest energy shell, that is, the n = 2 shell. The core electrons are in all the other (lower-energy) shells. Carbon has six total electrons: 1 s 2

• s

2

• p

2 . Therefore, the valence electrons are in the second shell, 2 s 2 and 2 p 2 , and the core electrons are in the first shell, 1 s 2 (noted in the figure by the circle and rectangle, respectively).Your Turn 1.3 Think What is the definition of bond energy? Looking at the plot of energy versus internuclear distance, what is the energy of the separate H atoms? What is the energy of the bonded H—H molecule? How does the bond energy correlate to these two values?Solve The bond energy represents the change in energy (on the vertical scale) needed to increase the bond length from its equilibrium value (the lowest energy point on the horizontal scale) to infinity. This can be estimated from the potential energy diagram (Fig. 1-11a). Using the energy difference of the separated H atoms ( E = 450 kJ/mol) and bonded H—H molecule ( E = 0 kJ/mol), a bond energy of 450 kJ/mol is estimated. 3 / 4

Your Turn 1.4 Think Look at Tables 1-2 and 1-3. Does the strongest bond have the largest or smallest kJ/mol value? In general, are single bonds stronger or weaker compared to double and triple bonds?Solve Stronger bonds have larger values for bond energy. Triple bonds tend to be stronger than single or double bonds.Your Turn 1.5 Think Lewis structures take into account only which type of electron? How are bonding and nonbonding electrons represented, and how are they counted? How do you determine whether a pair of electrons counts as part of an atom’s octet or duet?Solve For the electrons to be counted around any atom, the lines (bonding) or dots (nonbonding) have to touch the atom. The C atom’s octet (black dashed circle below) comprises the four sets of bonding electrons (lines) around the C atom. Each bond comprises two electrons shared between the atoms it touches. The O’s octet (black dashed oval below) comprises two sets of bonding electrons, one to the C atom and one to a H atom, and then two lone pairs. The H’s duet (gray dashed ovals) comprises the two shared electrons in the bond to either the C or O atom. You will notice that each bond contributes to the octet or duet simultaneously for each atom that touches the bond, hence the overlap for the circles/ovals.The strongest single bond has a value of 586 kJ/mol.a) The strongest single bond is the Si—F bond.b) The weakest single bond has a value of 138 kJ/mol.c) The weakest single bond is the O—O bond.d) The strongest bond of any type has a value of 1072 kJ/mol.e) The strongest bond of any type is the C≡O triple bond.f)

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