25 November AO vs MO

8/13/2019 25 November AO vs MO

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Atomic versus Molecular Orbitals in Comprehensive Introductory Organic Chemistry Textbooks

Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK, USA 73019

[email protected]

AbstractConsiderable variations, factual inaccuracies, inconsistencies of presentation, and ordering of various topics

related to atomic and molecular orbitals in various comprehensive introductory organic chemistry textbooksprompted us to compare commonly used textbooks for these inadequacies. This work is an effort in the

direction of improving the knowledge and understanding of atomic orbitals, molecular orbitals and related

concepts in introductory organic chemistry students. The comparison results and suggested remedies arepresented herein. The recommendations are fact-based, correct, pedagogically useful, and designed to remedy

discrepancies in comprehensive introductory organic chemistry textbooks. These recommendations will also

help to avoid the inadequacies from being carried on998888to the next textbook edition.

IntroductionUnderstanding atomic and molecular orbital characteristics is important to learning molecular structure

bonding, and reactivity. Because these are basic concepts for introductory organic chemistry, their accurate

presentation is critical in order for students to learn the subject. Therefore, inconsistencies in these concepts insome current comprehensive introductory organic chemistry textbooks can make it difficult for student learning

Accordingly, we have compared currently-used comprehensive organic chemistry textbooks in order to assess

their accuracy and consistency in presenting atomic and molecular orbital characteristics.In addition, the importance of topic sequencing in comprehensive introductory organic chemistry has been

highlighted recently.1 Therefore, we have also evaluated selected additional aspects of atomic and molecular

orbitals in these texts, including topic sequencing.

I. Atomic Orbital and Molecular Orbital CharacteristicsThere are a variety of atomic and molecular orbitals found in chemistry, and discussing them all is beyond

the scope of this article. Therefore, the atomic and molecular orbitals discussed herein are those which are mos

often found in organic chemistry.

A. Atomic OrbitalsAn atomic orbital (AO) is a theoretical region around an atomic nucleus where the probability of finding an

electron is high. The atomic orbitals which are most used in organic chemistry reactions are the familiar s, p

and d orbitals and f orbitals2(although h, g, i etc., the exotic high energy orbitals also exist theoretically).

B. Molecular Orbitals

Molecular orbitals, as the name implies, are orbitals representing the region of space occupied by electrons

in molecules.3a

A molecular orbital encompasses more than one nucleus and is obtained by combining atomic

orbitals in the molecule.3a

According to molecular orbital theory, there are two ways for orbital interaction to

occur: an additive interaction or a subtractive interaction. The additive interaction leads to formation of amolecular orbital that is roughly egg-shaped, whereas the subtractive interaction leads to formation of a

molecular orbital than contains a node between the atoms.3a

The overlap of two AO with matching symmetrysimilar energy, and close contact, forms two MOs, one lower-energy bonding MO and one higher-energy

antibonding MO, as shown in Figure 1.3a

The symmetry properties and relative energies of atomic orbitals

determine how the orbitals interact or mix to form molecular orbitals.3a,b

Atomic orbitals are less stable thanbonding molecular orbitals, but are more stable than anti-bonding molecular orbitals.

3a

Electrons are added to molecular orbitals, one at a time, starting with the lowest energy molecular orbital.3b

These molecular orbitals are then filled with the available electrons according to the same rules used for atomicorbitals; the overall energy of the electrons in the occupied molecular orbitals will be lower in energy than the

overall energy of the electrons in the original atomic orbitals, and the resulting molecule has a lower total
mailto:[email protected]:[email protected]:[email protected]


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energy than the separated atoms.3b

When the two atomic orbitals have quite different energies, the interaction is

weak, and the resulting molecular orbitals have nearly the same (energy and shape) as the atomic orbitals do (1sversus 2s, or 2s versus 2p).

3b Hybridized orbitals can also combine to form MOs provided they have matching

symmetries, have similar energies, and can make close contact. AO hybridization involves mixing AOs on an

atom to create hybrid AOs.3b

These new hybrid AOs allow for greater overlap when forming MOs. The

hybridization determines the shape of the molecule.3

1. Bonding Sigma Molecular Orbitals ()

The orbital resulting from overlap and constructive interference of atomic orbitals is called a bondingmolecular orbital, because electron(s) in this orbital spend most of the time in the region directly between the

two nuclei.3a,b

This orbital is called a sigma ( ) molecular orbital because it looks like an s orbital when viewed

along the axis of the bond.3a,b

Placing an electron in this lower-energy orbital (Figure 1) therefore stabilizes themolecule relative to the original atomic orbitals.

3a,b

2. Antibonding Sigma Molecular Orbitals (*)

The orbital resulting from overlap and destructive interference of atomic orbitals is called an antibondingmolecular orbital, because electrons placed in one of these orbitals spend most of their time in regions away

from the area between the two nuclei.3a,b

This orbital is therefore an antibonding, or sigma star ( *) molecular

orbital.3a,b

Because the * antibonding molecular orbital forces the occupying electron(s) to spend most of the

time away from the area between the nuclei, placing an electron in this higher-energy orbital makes themolecule less stable relative to the original atomic orbitals (Figure 1).

3a,b

3. Bonding Pi Molecular orbital ()Similarly to sigma bonding orbitals, a bonding molecular orbital should also result from two atomic

orbitals of appropriate shape and orientation to which result in formation of bond by sidewise overlapping.3c,d

So, either of two atomic pxor pyorbitals on a constructive overlap should result in bonding molecular orbital.A bonding pi orbital should have one nodal plane.

3c-e

4. Antibonding Pi Molecular Orbital (*)

A destructive interference of the orbitals involved in formation of bonding molecular orbital will result in

formation of antibonding * molecular orbitals.3c-e

The shapes of these orbitals are decided by the participatingorbitals in their formation. An antibonding * molecular orbital should have two nodal plane which result from

destructive interference of participating orbitals.3c-e

5. Nonbonding Molecular Orbitals (n)

The number of atomic orbitals which mix will equal the number of resulting molecular orbitals.3 If there

are three atomic orbitals of same symmetry and similar energy, the formation of three molecular orbitals isrequiredlow-energy bonding orbitals, high-energy antibonding orbitals, and intermediate energy nonbonding

orbitals).3 Atomic orbitals whose symmetries do not match, and therefore remain unchanged in the molecule

are also called nonbonding.3 If more than three atomic orbitals are involved, even then the number of atomic

orbitals will be equal to the number of molecular orbitals (i.e. bonding, antibonding, and nonbonding orbitals).3


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2p2p

2s2s

1s1s

antibonding orbitals

bonding orbitals


bonding orbitals


bonding orbitals

bonding andantibondingcancel out

big gap in energy here:the 1s orbitals are muchlower in energy than the 2s

energy

Figure 1. Schematic energy level diagram of MOs formed from interactions between the two atomic orbitals.

Methodology

We compared the ordering and content of material pertaining to atomic orbitals and molecular orbitalsacross thirteen

5-17current comprehensive introductory organic chemistry textbooks and two additional recently-

used ones,4,18

which were very popular while they were available. In order to do this, we (A) evaluated the

current edition of each textbook4-18

and (B) compared their presentations and drawings of atomic orbitals andmolecular orbitals, as well as the presentation orderings of atomic orbitals and molecular orbitals. Results are

shown in Table 1.

Results and DiscussionVariations in the order, descriptions, drawings, and comparisons of atomic orbitals and molecular orbitals are

found across these textbooks.4-18

Also, some texts had errors, which may be well-meant attempts to simplify thematerial, but which could nevertheless (1) confuse students who try to supplement the text with other materialor (2) leave students ill-prepared for questions on carbonyl chemistry in standardized tests, such as the ACS

standardized exam in organic chemistry.19

Also, recent changes in terminology have not been adopted

uniformly across textbooks.

Studies of Atomic Orbital versus Molecular Orbital.All textbooks explored herein (4-18) discuss and compare atomic orbitals versus molecular orbitals, but

some differ in the number of chapters presenting the topic (Table 1). Textbooks also differ in how early theconcepts are presented, as demonstrated by the chapter number in which AO and MO are presented. Jones (4)

Klein (6), Bruice (9), Solomons (10), Loudon (12), McMurry (15), Brown (16), and Vollhardt (17) present these

in the first chapter, while Hornback (8) and M Smith (13) discuss AO and MO in chapter three. Wade (5), JSmith (7), Carey (11), and Sorrell (18) spread the topics across two chapters, with the first being chapter one foratomic orbitals; Clayden (14) does the same, but starts later, in chapter four.


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correlation

with

figures

easy to

understand

preferred ->

Bruice Pearson 7 2013 1 21-27 9

Hornback Cengage 2 2006 3 61-68 8

Loudon Roberts 5 2009 1 23-39 12

Solomons Wiley 11 2013 1 27-37 10

Wade Pearson 8 2013 1,2 3-5,42-46 5

Klein Wiley 1 2012 1 13-17 6Vollhardt Macmillan 6 2011 1 23-30 N 17

Clayden Oxford Univ. 2 2012 4 80-101 N 14

Jones Norton 4 2010 1 31 N 4

Brown Cengage 7 2013 1 29-34 N 16

McMurry Cengage 8 2012 1 3-5,19-22 15

Carey McGraw Hill 9 2013 2 54-57 N N 11

M Smith CRC Press 1 2011 3 48-70 13

Sorrell Univ. Science 2 2006 2,10 49-51,307-311 N 18

J Smith McGraw Hill 4 2013 1,17 10,650-654 N N N N 7

captions

placement

in-text

maximizes

relevance

in-text description

Table 1. Atomic Orbi tals (AOs) vs Molecular Orbitals (MOs) in Introductory Comprehensive Organic Chemistry Textbooks

textbooks figures text

reffirst

authorpublisher

current

edition

pub

year

clear

definition

of AO &

MO

AO / MO

differentiation

included

AO vs MO

differentiation

clear

chapter page # present


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chapter page #

# of

figures

showing

node

# of

paragraphs

discussing

node

figure

accuracynode

nodal

plane

(planar

node)

others

preferred ->

Bruice 1 22-26 2 1.5 radial node 9

Hornback 3 62,66 1 1 spherical node / nodal sphere 8

Loudon 1,27 26-29,1338 4 5 spherical node / nodal sphere 12

Solomons 1 27,43 2 1 nodal surface 10

Wade 1 4 4 2 5

Klein 1 14 4 4 N 6

Vollhardt 1 24,29 2 3.5 17

Clayden 4 85,86 2 4 spherical node / nodal sphere 14

Jones 1 10-12,32 3 4 spherical node / nodal sphere 4

Brown 1 28 3 1 N 16

McMurry 1 4,20 0


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Most of these textbooks have appropriate figures captions except J Smith ( 7) where some AO and MO

figure captions are missing. Textbook figures should generally correlate well with the description given, andmost of these books follow this, except for one (18), where the figures do not quite match the description given

in the text. Figures should help students understand the concept by visualization, so the figures should be easy

to understand. However, the figures in some texts are somewhat difficult to understand (4,7,10,11,13,15,17,18)

while others are relatively easy (5,6,8,9,12,14,16).

Upon reviewing the figure accuracy for the most recent textbook from Brown it was noted, in Table 2, that

the response should be changed from a Yes to a "No". The reasoning behind this decision can be found onpages 34,35, and 36 with the figures (a) of 1.12, 1.14, and 1.16 all depicting the cartoon version of atomic

orbitals for sp, sp2, and sp

3to all be identical; however, the computerized versions of these images all show the

slight similarities that actually exist between these types of atomic orbitals. For the same column of Table 2 thetextbook from M. Smith was also found not to be incorrect, but incomplete. Although figure 3.1 correctly

depicts the orbital images and their nodes from wave functions, the shapes of the nodes for the atomic orbitals

are not shown in a manner that is easy to understand. There are some 2-D versions showing possible shapes for

these orbitals but a 3-D depiction would convey a much clearer message. After checking "node" column underthe term, in Carey book in Table 2, believed that book should be "N" because in page 56 figure 2.5 b, node is

mentioned in figure only but not in text. After examination " easy to understand" column under the

hybridization in M Smith book in Table 3, the sentence moving from page 62-63 mentions "blue lobes" where

the lobes should have been termed "orbitals". For example "The hybridization process is illustrated by the "bluelobes" for electrons in the 2p-orbitals "donated" by carbon and the "red lobe" the electrons in the 2s-orbital" also

the colors of the figures do not match. So this column is filled with "N".

After further review, it was determined that the in-text descriptions of the J Smith and Carey books were

not easy to understand. In J Smith, page 651 Section: 17.9A the orbitals have combined to form a single colored

mass for the lower bonding MO and two separate MOs for the antibonding MO. In the in-text description inSection: 17.9B the author states "Because each of the six carbon atoms of benzene has ap orbital, six atomic

porbitals combine to form sixpimolecular orbitals" in reference to figure 17.9. In this instance the author does

not follow his previous representations of atomic orbitals combining into molecular orbitals. Notice that when

the 6porbitals combine into the benzene model the orbitals are still depicted as the author had previously

referred to as atomic orbitals. The bonding MOs appear to be single atomic orbitals instead of molecularorbitals. They show no orbital overlap.

In Carey, on pages 372 and 373, the definitions of AO and MO are poorly introduced in a complicated and

alternative approach. The text is difficult to understand because the descriptions appear unclear. While

describing one situation, another is introduced in the middle. The author uses too much description of the

figures and not enough information on the theories. There are sentences that are fairly complex by includingseveral clauses. This appears distracting and makes it difficult to follow the thought. For example Recalling

from section 2.4 that the number of orbitals is equal to the number of atomic orbitals (AO) that combine to form

them, we combine the three 2p AOs , one from each of the three sp2- hybridized carbons of allyl, into the

system of three MOs shown in figure 10.2 (pp 373).

Upon reviewing the data for the in-text descriptions of figures under the easy to understand column in

Table 1, it was determined that the Jones, M Smith, McMurry, and Vollhardt textbooks in-text descriptions ofthe figures were easy to understand; thus, the response should be changed from N to Y.

Analysis of the Clayden textbook determined that there are no captions for the figures on pages 80-101;therefore, under the captions column of Table 1, the absence of captions should be denoted by an N. The

textbook explains the figures with in-text description, however there are no captions to emphasize the points

mentioned in the text.


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Under the heading figures and subheading placement in-text maximizes relevance, in Table 1 for the

Vollhardt and Brown textbooks, the placement of figures in the text does not seem to maximize relevance andshould be denoted by an N. In Vollhardt, the in-text description of Figure 1-7 on page 26 mentions p-orbital

diagrams, but the Figure is of an s orbital. The text describes the three rules for assigning electrons to atomic

orbitals, on page 27 and notes Figure 1-8 as an example. However, Figure 1-8 only gives an example of an

empty energy level diagram. Figure 1-9 provides an example of filled energy diagrams, but the textbook doesnot provide enough examples for the atomic orbital diagrams. In Brown, for Figure 1.21, the bottom cartoon

representation of the in-phase addition is incorrect. The molecular orbital should connect if the atoms are in-

phase as shown in the computed representation.Also, for Figures 1.12, 1.14, 1.16 on pages 34, 35, 36, thecartoon representations ofsp

3,sp

2, andspare identical to each other, while the computed representations

are different from each other. The size of the smaller lobe on each of the computed representations decreases

as thescharacter increases in these hybridized orbitals.

In J Smith, on page 652, section 17.9B, the in-text descriptions are correct, however Figure 17.9 appears to

be incorrect. It describes the interactions of atomicporbitals of benzene as molecular, but it does not show the

actual molecular orbitals. This makes it difficult for this reader to understand what type of orbitals are beingrepresented in the figure. The lack of continuity throughout the section concerning the depiction of AO vs. MO

leads for the N in the column AO vs. MO differentiation clear.

In M. Smith -- section 3.1.2, page 52atomic orbitals are discussed, but they are not clearly defined.Molecular orbitals, however, are clearly defined on page 57, section 3.3.

M. Smith should be changed from No to Yes in the columns of clear definition of MO and AO along

with the column AO and MO clear differentiation. These examples from the book will explain why the change.Because bonds are found in molecules, the orbitals used to form a bond in the molecule are differentfrom the

orbitals found in elemental atoms (52). For an isolated atom of a given element, the electrons are in atomic

orbitals (Figures 3.1, 3.2 and 3.4), but in a molecule, the electrons reside in different orbitals known as

molecular orbitals(56). The orbitals used to form covalent bonds in molecules are called molecular

orbitals(and are different from atomic orbiats) . . . (57). In other words, molecular orbitalsare different in

energy when compared to the corresponding atomic orbitals (58). These quotes from the book give a

definition for AO as well as MO. The AO definition is not bolded not italicized like MO but it is in the text.

M. Smith makes it a point to ensure that the reader knows that MO is NOT the same as AO in several placesthroughout the chapter as can be seen in the examples above.

In Sorrell, on pages 49-50, section 2.4b, a clear definition of atomic orbitals does not seem to be given

before it is used to define the valence bond theory. Furthermore, the definition of valence bond theory seems

similar to the definition of molecular orbital theory, which is not mentioned for almost three hundred pages.

Also, while the diagrams are correct, they seem difficult to understand because they are represented in differentshades of pink. They would be clearer if the figures were not in the same color.

Changing N to Y on table for differentiation of AO vs MO and clear differentiation. In Sorrell, there is a

clear definition given of atomic orbitals and they are explained furthermore in the description of valence bond

theory. Although the description and definition of molecular orbitals are not presented until later on (roughly

two hundred eighty pages), they are presented in a clear and concise manner. When two atoms come together,each contributes an atomic orbital toward bond formation, then two molecular orbitals are combined. (Page

307) Also on page 307, molecular orbitals are said to be mathematical constructions of atomic orbitals. Thediagrams are correct, but they do seem to cause confusion due to the fact that they are monocolored despite

depicting different types of atomic and molecular orbitals.

Another aspect of Careys text that makes it difficult to understand is that in this section, which is supposed

to describe atomic and molecular orbital theory, seems to not explicitly state their respective definitions.

Although in section 2.4 there is an accurate description that is referenced, atomic and molecular theory is notrestated in chapter 10.1, which should be its appropriate location. The section should be revised and the


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information should be reformatted in a way that clearly presents the main ideas in a simpler writing style under

the figures instead of in the text.

The definition of atomic orbital and molecular orbital is very clear in some textbooks (5,6,8-12,14-17)

while others (4,7,13,18) do not define them so clearly. All books (4-15,18), except for two (16,17), have

relevant figures. Most textbooks discuss the differentiation between Atomic Orbital versus Molecular Orbita(4-6,8-17) except two (7,18) which skip the differentiation completely. Figure references in all the texts are

correct. Description and presentation of AO node and MO node is shown in Table 2. The texts differ in the

chapter number in which AO node and MO node are presented. Jones (4), Klein (6), J Smith (7) Bruice (9)Solomons (10), Carey (11), McMurry (15), Brown (16), Vollhardt (17) discuss them in the first chapter

Hornback (8) presents them in chapter three, while the description of node is spread across two chapters in

Clayden (14), Wade (5), Loudon (12), M Smith (13), Sorrell (18). We recommend presenting node in onechapter at the introduction of atomic orbital structure, because spreading the discussion across many chapters

unnecessary splits this closely related information. Overall, the concept of node is explained clearly in all the

books (4-10, 12-18), except one (11).

The use of different names for node, such as node of electron density, nodal surface, radial node, and

planar node was found during the study. One textbook (7) used both terms node, and node of electron

density interchangeably, which could lead to confusion. We recommend using node consistently

throughout, because node of electron densitymight lead a student to think the exact opposite to the fact thatthe node actually has no electron density. Two books (10,11) use nodal surfacein addition to nodewhen

presenting the area of no electron density, but one book (9) separately defines radial node. Most textbooks

(4,5,8-10,12,14,16,17) explain planar node or nodal plane while six books (6,7,11,13,15,18) completelyoverlook this. In addition to the above mentioned terms, Jones (4), Hornback (8), Loudon (12), and Clayden

(14) use the terms spherical node or nodal sphere. Explaining nodal plane is extremely important to

understanding the shapes of orbitals, so it is strongly recommended that this be included in all such textbooks.The textbooks also differ in the number of figures used to explain the concept of AO and MO. Wade (5)

Bruice (9), Solomons (10), Clayden (14), and Vollhardt (17) use two figures to explain them, while Jones (4)

and Brown (16) use three, and Klein (6) and Loudon (12) use four. Three books JSmith (7), Hornback (8)

Carey (11), and M Smith (13) use one figure to discuss node, while McMurry (15) and Sorrell (18) use no

figures at all to explain the concept of node.An appropriate description in addition to a figure is also required in order to clearly present the concept

node. However, different textbooks have different amount of text for explaining node. It is difficult to say howmany paragraphs should be used to explain the concept of node, but the descriptive text should be enough to

explain the characteristics of the node, so that it is clear and does not overwhelm students. Jones (4), Klein (6)

Clayden (14), and Vollhardt (17) have four paragraphs, while Bruice (9) uses one and one-half paragraphs

Hornback (8), Solomons (10), and Sorrell (18) explain all properties of a node in one paragraph, while Wade(5), J Smith (7), Carey (11), and McMurry (15) do not devote a complete paragraph to this.

Although Jones (4), Wade (5), Klein (6), Hornback (8), Bruice (9), Loudon (12), M Smith (13), Brown

(16), and Vollhardt (17) present accurate information about node by using merely figures alone, but J Smith ( 7)

Solomons (10), Carey (11), and Vollhardt (17) do not have such a clarity in explanation about node. Similarly

nine textbooks (4-6,8-10, 13, 16, 17) present appropriate terms for the explanations, while (7,11, 12, 14, 15)have not used the appropriate terms. Some books (4,5,12,14,16) use multiple terms as mentioned above and

clearly define and differentiate each of them, while the others (7,9,10,13,17) use multiple terms, but do notdefine and differentiate them.

The concept of hybridization is key in understanding the shape and geometry of a molecule. Klein (6), J

Smith (7), Bruice (9), Solomons (10), Loudon (12), McMurry (15), Brown (16), and Vollhardt (17) discuss thisconcept in the same chapter with atomic orbitals, while, Jones (4), Wade (5), Carey (11), and Sorrell (18)

present it in the chapter immediately following atomic orbitals. Hornback (8), Clayden (14), and M Smith (13)

place this in chapter 3, and M Smith split the discussion into chapters 3 and 5. We recommend thathybridization should be discussed in the same chapter with atomic orbitals, in order to better understand the


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concept, at a time when atomic orbitals are still fresh in students minds. All of the text books (4-13,15-17)

used appropriate terms in illustration of hybridization with the exception of Clayden (14), Sorrell (18).All textbooks used appropriate figures, which have accurate captions and text descriptions for explaining

hybridization. Except for Loudon (12), M Smith (13), and Clayden (14), all books present the concept in a way

such that it is easy for students to understand. Surprisingly, only Wade (5), Brown (16), and Sorrell (18) refer

to VSEPR theory for the hybridization, while the others do not.

chapter page #easy to

understand

reference

to VSEPR

theory

ref

preferred ->

Bruice 1 27-35 9

Hornback 3 69-77 8

Loudon 1 15, 37-41 12

Solomons 1 32-38, 44 10

Wade 2 46-55 5

Klein 1 18-23, 25 6

Vollhardt 1 31-36 17

Clayden 4 99-103 N 14

Jones 2 52-60 N 4

Brown 1 23-25, 32-36 16

McMurry 1 11-17 N 15

Carey 2 24-27, 54-65 11

M Smith 3, 5 62-63, 123-125, 128-130, 140 N 13

Sorrell 2 51-62 18J Smith 1 25-40 7

Table 3. Hybridization Characteristics in Various Introductory Comprehensive Organic

Chemistry Textbooks

first author

hybridization

Aromaticity vs Pericyclic reactions:For explaining aromaticity as well as the stereochemistry in pericyclic reactions both atomic and molecular

orbital plays a central role. Molecular orbital theory also enables to understand aromaticity and predicting thestability of aromatic systems. So, it becomes important to compare the textbooks for presentation of aromaticity

and pericyclic reactions with atomic and molecular orbitals. Aromaticity is explained before pericyclic reactions

in nine text books. McMurry (15), Hornback (8), Bruice (9), Clayden (14), Loudon (12), J Smith (7), M Smith

(13), Jones (4), Brown (16) while pericylic reactions are discussed before aromaticity in six books Klein (6)Sorrell (18), Vollhardt (17), Solomons (10), Carey (11), Wade (5). Aromaticity should be discussed before

pericyclic reactions because it will help in understanding the transition state of pericyclic reactions. As thetransition state has continuous flow of electron and resulting into its stabilization it is extremely important that

student must know what imparts stability to a conjugated system of continuous flowing electrons. So, werecommend presenting aromaticity before pericyclic reactions and conjugated system. The Vollhardt (17) book

only discusses electrocyclic reactions.

Different books have different lengths of separation between aromaticity and pericyclic reactions discussions

Wade (5) presents aromaticity immediately followed by pericyclic reactions (1 chapter length apart), Brown

(16), M Smith (13) has a three, Hornback (8) has a six, Jones (4) has seven, J Smith (7) has a, Loudon (12) has atwelve, McMurry (15) has a fifteen, Bruice (9) has twenty, and Clayden (14) has a twenty six chapters


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separation. Furthermore, the M Smith (13) book focuses on sigmatropic rearrangements. Unless purposely

paired together by the instructor both sets of material will not be taught in organic chemistry I.

Twelve books McMurry (15), Hornback (8), J Smith (7), M Smith (13), Vollhardt (17), Sorrell (18), Solomons

(10), Carey (11), Klein (6), Wade (5), Brown (16) explain aromaticity in benzene & aromatic compounds

chapter. Eight books Clayden (14), Loudon (12), McMurry (15), Hornback (8), J Smith (7), M Smith (13)Jones (4), and Bruice (9) discuss pericyclic reactions separately while Vollhardt (17), Sorrell (18), Solomons

(10), Carey (11), Klein (6), Wade (5) discuss it with conjugated pi-electron systems.

Clayden (14) is the only book which discusses pericyclic reactions in two chapters while rests of the booksdiscuss it in one chapter either alone or with pi-conjugated systems. Brown (16) presents the pericyclic reaction

with other C-C bond formation reactions, which include several charge controlled reactions in addition to

orbital controlled pericyclic reactions.

Conclusions

Comparing fifteen currently used comprehensive introductory organic chemistry textbooks reveals

discrepancies, variations, and inconsistencies in their presentations, figures, and discussions of their atomicorbital and molecular orbital concepts. Recommendations with appropriate and reasonable justifications have

been provided in order to remedy these shortcomings. In order to facilitate studentslearning these concepts, we

provide recommendations which should be pedagogically useful, consistent, descriptive, and in agreement with

research literature.

References

1. Houseknecht, Justin B. Topic Sequence and Emphasis Variability of Selected Organic Chemistry TextbooksJ. Chem. Educ. 2010, 87, 592-597.

2. (a)Hoogenboom, Bernard E. Three Dimensional Models of Atomic Orbitals. J. Chem. Educ. 1962, 39,40

41. (b) Graham, Donald M. A 3-D Diagram of the Relationships among Atomic Orbitals. J. Chem. Educ

1996, 73, 210. (c) Cohen, Irwin; Bustard, Thomas.J. Chem. Educ.1966, 43, 187-193.

3. (a) Thompson, H. Bradford. Dynamic Projector Display for Atomic Orbitals and the Covalent Bond.J

Chem. Educ. 1960, 37, 118 - 121. (b) Cohen, Irwin; Del Bene, Janet.J. Chem. Educ.1969, 46, 487-492. (c)

Yves Jean; Francois Volatron. An Introduction to Molecular Orbitals; Oxford University Press, 1993. (d)

Autschback, Jochen. J. Chem. Educ. 2012, 89, 1032-1040. (e) Herndon, William C.; Silber, ErnestoSimplified Molecular Orbitals for Organic Molecules.J. Chem. Educ.1971, 48, 502-508.

4. Jones, Maitland Jr.; Fleming, Steven. A. Organic Chemistry, 4th ed.; W. W. Norton & Co. Inc.: New York,NY, 2010.

5. Wade, Leroy G. Jr. Organic Chemistry, 7th ed.; Pearson Education, Inc.: Upper Saddle River, NJ, 2010.6. Klein, David. Organic Chemistry,1st ed.; John Wiley & Sons, Inc.: New York, NY, 2012.7. Smith, Janice G. Organic Chemistry, 3rd ed.; John Wiley & Sons Inc.: New York, NY, 2011.8. Hornback, Joseph M. Organic Chemistry, 2nd ed.; Thomson Learning, Inc., Brooks/Cole: Belmont, CA

2006.

9. Bruice, Paula Y. Organic Chemistry, 7th ed.; Prentice Hall: Upper Saddle River, NJ, 2013.10.Solomons, T. W. Graham; Fryhle, Craig B.; Snyder Scott A. Organic Chemistry,11th ed.; John Wiley &

Sons, Inc.: New York, NY, 2013.11.Carey, Francis A.; Giuliano, Robert M. Organic Chemistry, 8th ed.; McGraw-Hill: New York, NY, 2011.12.Loudon, Marc. Organic Chemistry, 5th ed.; Oxford University Press: New York, NY, 2009.13.Smith, Michael B. Organic Chemistry, 1st ed.; CRC Press Taylor & Francis Group, LLC: Boca Raton

2010.

14.Clayden, J.; Greeves, N.; Warren, S. Organic Chemistry,2nd ed.; Oxford University Press: New York, NY,2012.

15.McMurry, John. Organic Chemistry, 8th ed; Brooks/Cole: Belmont, CA, 2012.16.Brown, William H.; Foote, Christopher S.; Iverson, Brent L.; Ansyln, Eric V. Organic Chemistry, 5th ed.

Brooks Cole Publishing: Pacific Grove, CA, 2009.


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17.Vollhardt, K Peter C.; Schore, Neil E. Organic Chemistry, 6th ed.; W. H. Freeman and Co.: New York, NY2011.

18. Sorrell, Thomas N. Organic Chemistry, 2nd ed.; University Science Books: Enfield, NH, 2006.21.ACS Standardized Exam.

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25 November AO vs MO