CHEM 3361 EXAM 1

In an optimal Lewis structure for azide ion (N3-, which is linear), what is the formal charge on the central nitrogen?

+1

What is the net formal charge on the following Lewis structure (meaning, the sum of all formal charges)? All valence electrons are shown.

0

In an optimal Lewis structure for ethyne, HCCH, how many of the valence electrons are bonding electrons? (The connectivity is H C C H.

10

How many moles of O2 would be needed for the complete combustion of 1 mole of methycyclohexane?

10.5

Exactly how many hydrogens are present in the molecule 1,1,5-trichloro-2-methylpentane?

11

How many lines are present in a simple bond-line structure of cyclopentyl-cyclooctane?

14

How many electrons does an isolated neutral sulfur atom have?

16

Of these four, which solution is the most basic (least acidic)?

1M NaOCH3 (The pKa of HOCH3 is 15.2.)

How many stereocenters are present in the following molecule?

2

Which molecule is not a constitutional isomer of the others?

2,3,3-trimethylpentane

Which molecule, a-d, is not a constitutional isomer of cyclopentene?

2-Methyl-2-butene (this question shouldn't be here)

How many hydrogen atoms are present in the following molecule?

20

Exactly how many hydrogens are present in the following molecule?

22

How many tertiary carbons are present in cis-1-isopropyl-3-methylcyclopentane?

3

How many valence electrons are there in a neutral molecule of formula C3H4F2?

30

How many valence electrons are present in a neutral molecule of formula C3H5FO2?

36

How many constitutional isomers have the formula C4H9F?(Hints: Name them! Fluorine makes only one bond at a time. None of the isomers have rings or double bonds.)

4

How many electrons in total are in an isolated, neutral beryllium atom (Be)?

4

In an optimal Lewis structure for hydrogen peroxide, HOOH, how many lone pairs are present?

4

How many cycloalkanes have the atomic formula C4H7Br? (Consider constitution and cis/trans isomers.)

5

How many protons are in a boron nucleus?

5

How many secondary carbons are present in ethylcyclopentane?

5

How many valence electrons are there in an isolated, neutral phosphorus atom?

5

In either chair conformation of trans-1,3-difluorocyclohexane, how many of the hydrogens are axial?

5

How many moles of molecular oxygen are needed for the complete combustion of one mole of C4H8O?

5.5

How many 1s orbitals are shown in a proper valence-bonding diagram for cyclopropane?

6

How many protons are in a carbon nucleus?

6

In an optimal Lewis structure for hydroxide ion, OH- , how many valence electrons are unshared?

6

What is the proper IUPAC name of the following molecule?

6-ethyl-3-methylnonane

For the clean combustion of one mole of 3,3-diethylpentane, what is the ratio of products?

9 CO2+ 10 H2O

The reaction of HCl with a C=C bond generally proceeds by:

A MIXTURE OF SYN AND ANTI ADDITIONS

Is the following molecule chiral or achiral?

ACHIRAL

As you know, electronegativity increases from left to right and from bottom to top in the periodic table of elements. So, of the following, which is the most electronegative element?

B

By VSEPR theory, what is the expected molecular geometry at the oxygen atom in H2NOH? (Hints: Draw the Lewis structure. The connectivity is H2N O H.)

BENT

Which of the following can exist as cis/trans isomers?

BOTH A AND C (1-chloro-2-methylcyclopropane AND 1-bromo-2-chlorocyclopropane)

Which formula indicates saturation?

C11H24

What substitution product should I expect in reacting 1-chloro-5-fluoropentane (ClCH2CH2CH2CH2CH2F) with NaCN?

C6H10NF

Is the following molecule chiral or achiral?

CHIRAL

What's the general formula for a hydrocarbon that has two rings in its structure (and no other kinds of unsaturation)?

CnH2n-2

What is the relationship of the following molecules?

DIASTEREOMERS

What is the relationship of the following molecules?

ENANTIOMERS

Which combination is most likely to give an E1 (as opposed to an E2) mechanism?

EXCELLENT LEAVING GROUP WITH WEAK BASE

Of the following, the strongest Brønsted acid is:

H2O

Which of the following species has a non-zero dipole moment? (Assume that all of the elements in this problem have at least slightly different electronegativities from one another.)

H2O

Which of the following is a BrØnsted acid and a conjugate base?

H2O and HOSO3-

Which acid is weakest?

HF

Of the following, which acid has the lowest pKa?

HI

What is the relationship of the following molecules?

IDENTICAL

Imagine a simple SN1-type reaction involving water (as nucleophile) and 2-iodobutane as electrophile. If you double the concentration of each of these reactants in a second trial, how will the reaction rate be affected?

IT WILL DOUBLE

Which is the 12th element in the periodic table?

Mg

In the full Lewis structure for cation H-O-CΞN-F (which contains 22 valence electrons in total), the formal plus charge is on:

N

If the enthalpy of reaction for a given transformation is negative and the entropy of reaction is positive, then the free energy of reaction will be:

NEGATIVE

Which is element number 7 in the periodic table?

NONE (B, F, Ne)

What is the proper IUPAC name of the following molecule?

NONE OF THESE (2-ethyl-5-methylheptane 3-methyl-6-ethylheptane 6-ethyl-3-methylheptane)

What is the proper IUPAC name of the following compound?

NONE OF THESE NAMES ARE RIGHT (1-methyl-1-cyclopropylbutane 2-methyl-2-cyclopropylbutane 1-cyclopropyl-1,1-dimethylpropane)

Which substance has NO constitutional isomers?

PROPANE

A Brønsted base is a:

PROTON ACCEPTOR

Which of the following statements is FALSE?

Reaction catalysts work by altering the position of equilibrium.

The configuration of stereocenters in the following molecule (left to right) is:

S , R

Which type of alkyl bromide generally affords the fastest rates in SN1 reactions?

TERTIARY

What is the molecular geometry at carbon 2 in 2-methylpropane? (Hint: draw the full Lewis structure.)

TETRAHEDRAL

Klein says that addition reactions to C=C bonds are generally performed at low temperatures because:

THE ENTROPY OF REACTION FOR ADDITIONS IS LEAST UNFAVORABLE AT LOW TEMPS

Which of the following is generally a poor choice of leaving group for an SN2 process?

THESE ARE ALL FINE (bromide ion iodide ion tosylate)

Which of the following is NOT a proper IUPAC name?

THESE ARE ALL GOOD - cyclohexylcyclohexane - ethylcyclobutane - 1-bromodecane

According to VSEPR analysis, what's the molecular geometry around the phosphorus atom in PBr3? Assume that a bromine can make only one bond at a time

TRIG. PYRAMIDAL

Please provide each of the following: a)Three resonance structures for nitric acid, HNO3, in which all atoms (except H) obey the octet rule. N is central, directly bonded to all three oxygens. The H is attached to one oxygen. Show any formal charges. b) One simple molecule with a strong net dipole (and label it 'polar') and one simple molecule with no net dipole (and label it 'non-polar')

b) H-F polar ; H-H non-polar

Which molecule has exactly one primary carbon?

butylcyclobutane

We can expect a Brønsted acid to have:

one MORE proton than its conjugate base

When working with any specific acid, it's important to remember that:

pH is adjustable and pKa is fixed

Of the following, which alkyl halide will generally give the worst ratio of SN2- type substitution over elimination?

tert-butyl chloride

Which of the following is not a proper IUPAC name?

trans-1,3-dibromohexane

Which compound CANNOT follow Markovnikov's rule in adding HCl?

trans-3-hexene