I. STRUCTURE, BONDING, & RESONANCE TEST 1

1 / 19

Relative to neutral ¹⁶O in the same bond pattern, what changes?

¹⁸O in CH₃-¹⁸O-H: Z=8

2 / 19

A mass spectrometer distinguishes these molecules. Which pair of atomic properties explains the difference?

¹³CH₃-CH₂-OH and ¹²CH₃-CH₂-OH

3 / 19

A proposed carbon 2p orbital has no nodal plane through the nucleus. What is the defect?

Isolated carbon: 2s and 2p orbitals

4 / 19

A drawing rotates 2px into the orientation formerly labeled 2py. Which property remains the same?

Isolated atom: 2px, 2py, 2pz; no external field

5 / 19

Which electron count is used for oxygen before allocating bonds in a Lewis structure?

CH₃-O-H; neutral O: 1s2 2s2 2p4

6 / 19

Which occupancy minimizes energy under the usual Hund model?

Three degenerate 2p orbitals; two electrons

7 / 19

What spin is allowed for a second electron occupying that same orbital?

One spatial orbital: electron 1 has ms=+1/2

8 / 19

A student assigns zero formal charge to O. Which bookkeeping correction is needed?

CH₃-O⁻; O has three lone pairs

9 / 19

Which accounting supports the displayed charge?

(CH₃)₄N⁺; four N-C bonds, no N lone pair

10 / 19

Which electron-bookkeeping move could complete the central carbon's octet without adding an atom to the species, even if energetically unfavorable?

(CH₃)₃C⁺; three C-C bonds

11 / 19

An additional H⁺ protonates the carboxylate. What is the product's net charge?

H₃N⁺-CH₂-C(=O)-O⁻

12 / 19

Why is the second carbon invalid as drawn?

Proposed CH₃-C(H)(H)(H)-OH with all drawn bonds single

Proposed drawing: all bonds shown are single

13 / 19

How many sigma and pi bonds join the three heavy-atom pairs shown?

Three heavy-atom bonds

14 / 19

How does the number of electrons in carbon-carbon pi bonds change?

HC#CH -> H₂C=CH₂, one H₂ added

One equivalent of hydrogen added

15 / 19

Which motion most directly destroys their pi overlap?

Two parallel p orbitals perpendicular to a C-C axis

Two parallel p orbitals on adjacent carbon atoms

16 / 19

Which local geometry is expected at the carbonyl carbon?

17 / 19

What is the approximate C-C-C angle at the middle carbon?

18 / 19

After constructing its sp hybrids, how many p orbitals remain for pi bonding?

H-C#N; consider the carbon atom

19 / 19

How many carbon atoms are sp hybridized?

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I. STRUCTURE, BONDING, & RESONANCE TEST 2

1 / 20

Why is the C-O-C bond angle associated with a bent molecular arrangement at O?

CH₃-O-CH₃; two O bonds and two O lone pairs

2 / 20

Which explanation predicts the C-C length trend?

CH₃-CH₃; CH₂=CH₂; HC#CH

3 / 20

In a direct thermal rotation model, which energetic cost is central?

CH₃-CH=CH-CH₃, E form -> Z form

Rotation about the central double bond

4 / 20

Where should the arrow for formation of the O-H bond begin?

CH₃-O⁻ + H-Br

O-H bond formation: reactants

5 / 20

Which electron allocation describes the bond cleavage?

Br-Br –light–> 2 Br radicals

Homolytic cleavage

6 / 20

What is conserved in this heterolytic bookkeeping step?

CH₃-Br -> CH₃⁺ + Br⁻, idealized cleavage

Idealized heterolytic cleavage

7 / 20

What remains fixed between these resonance contributors?

CH₃-C(=O)-O⁻ <-> CH₃-C(-O⁻)=O

8 / 20

A prediction assigns two distinct C-O bond lengths to the actual isolated ion solely from one contributor. What is the correction?

Two equivalent resonance drawings of CH₃CO₂⁻

9 / 20

With both contributors satisfying octets, why is the O-negative contributor often weighted more?

Enolate contributors: CH₂=C(O⁻)-CH₃ and (-)CH₂-C(=O)-CH₃

10 / 20

Which structural feature explains greater charge delocalization in the first ion?

CH₃-C(=O)-O⁻ and CH₃-CH₂-O⁻

11 / 20

Which proposed observation follows from N-lone-pair conjugation?

12 / 20

Under the ordinary nonconjugated carbocation model, what stabilizes the first cation?

(CH₃)₃C⁺ compared with CH₃CH₂⁺

13 / 20

Which contributor is obtained by moving only the pi pair toward the cationic end?

CH₂=CH-CH₂⁺

14 / 20

A proposed hydride shift moves H from the adjacent CH carbon. Which test supports the proposal?

CH₃-CH⁺-CH(CH₃)-CH₃

15 / 20

Why is direct benzylic conjugation available only to the first radical?

C₆H₅-CH₂ radical and C₆H₅-CH₂-CH₂ radical

16 / 20

What fraction of the modeled monohalogenation events occurs at type b?

Model substrate: 9 type-a H and 1 type-b H; per-H rates 1 and 9

a: 9 H total (three methyl groups); b: 1 H. Per-H rates: a = 1, b = 9.

17 / 20

Which two electron-pair moves avoid exceeding carbon's octet?

CH₃-C(=O)-CH₃ + H⁻, first addition step

First nucleophilic addition step

18 / 20

Why can these drawings not be resonance contributors?

CH₃-C(=O)-CH₃ and CH₂=C(OH)-CH₃

19 / 20

What changes when a base removes only the O-H proton?

CH₃-O⁺(H)-CH₂CH₃; O has one lone pair

O-H proton removal

20 / 20

From left to right, what are the hybridizations of the three carbon atoms?

CH₃-C(=O)-C#N

Read the three carbon atoms from left to right

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