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Chapter 1
Introduction and Review

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01-02

Title	Electron Density Diagram of the 1s Atomic Orbital
Caption	Figure 1-2Graph and diagram of the 1s atomic orbital. The electron density is highest at the nucleus and drops off exponentially with increasing distance from the nucleus in any direction.
Notes	The electron density is highest at the nucleus and drops off exponentially with increasing distance from the nucleus in any direction.
Keywords	1s atomic orbital, nucleus, electron density

01-03

Title	Electron Density Diagram of the 2s Atomic Orbital
Caption	Figure 1-3The 2s orbital has a small region of high electron density close to the nucleus, but most of the electron density is farther from the nucleus, beyond a node, or region of zero electron density.
Notes	There is a node separating two electron density regions in the 2s orbital. The majority of the electron density can be found on the outer ring.
Keywords	2s atomic orbital, electron density, nucleus, node

01-04

Title	Representations of the 2p Orbitals and its Electron Density Diagram
Caption	Figure 1-4 The 2p orbitals. There are three 2p orbitals, oriented at right angles to each other. Each is labeled according to its orientation along the x, y, or z axis.
Notes	Each p orbital consists of two lobes.
Keywords	2p atomic orbitals, lobes, node, nodal plane, degenerate orbitals

01-05-03UN

Title	Lewis Structure and Extended Structure of Methane
Caption	A covalent bond is usually represented by a dash between the atoms that share those electrons.
Notes	While in Lewis structures a bond is represented with two dots, in the extended formula it is represented with a dash. Each dash counts for two electrons so a single bond is one line (2 electrons), a double bond is represented by two lines (4 electrons) and a triple bond by three lines (6 electrons).
Keywords	Lewis structure, octet rule, covalent bond, extended structure, extended formula, methane, ethane

01-05-05UN1-3

Title	Lewis Structures of Compounds with Lone Pairs of Electrons.
Caption	As the following structures show, there is a lone pair of electrons on the nitrogen atom of methylamine, and there are two lone pairs on the oxygen atom of ethanol. Halogen atoms usually have three lone pairs, as shown in the structure of chloromethane.
Notes	A correct Lewis structures must show all pairs of electrons, bonded and non-bonded. Organic chemists often do not show the lone-pairs of electrons to save time.
Keywords	lone pairs, non-bonded pairs, methylamine, ethanol, chloromethane

01-05-06UN

Title	Lewis Structure of Compounds with Double and Triple Bonds.
Caption	The following are examples of organic compounds with double bonds. In each case, four electrons (two pairs) are shared between two atoms to give them octets. A double dash (=) is used to symbolize a double bond.
Notes	Atoms can share more than one pair of electrons in order to complete their octet. Sharing two pairs of electrons is called a double bond and it is represented by two lines in the extended formula; sharing three pairs of electrons is called a triple bond and it is represented by three lines.
Keywords	double bond, triple bond, carbonyl bond, lone pairs, octet rule, octet, valence bonds

01-05-09UN

Title	Bonding Patterns for Carbon, Nitrogen, Oxygen, Hydrogen and Halogens
Caption	Common bonding paterns for the most used elements in organic chemistry. Carbon is tetravalent, nitrogen is trivalent, oxygen divalent. Hydrogen and the halogens are both monovalent but while hydrogen obeys the duet rule, the halogens have a complete octet with three lone pairs of electrons around them.
Notes	Carbon needs to form four bonds to complete its octet so it is referred to as tetravelant. Nitrogen will usually have three bonds and one lone pair of electrons (trivalent), while oxygen forms two bonds and has two lone pairs of electrons (divalent). Hydrogen obeys the duet rule so it will only form one bond (monovalent). Halogens form only one bond and have three lone pairs of electrons.
Keywords	valence bonds, lone pairs, tetravalent, trivalent, divalent, monovalent, duet rule, octet rule

01-07

Title	Pauling Electronegativity Scale for Selected Elements
Caption	Figure 1-6The electronegativities of some of the elements found in organic compounds.
Notes	Electronegativity is a guide for predicting the polar nature of bonds and the direction of their dipole moment. The more electronegative the atom, the more they "pull" the bonding electrons toward them. The most electronegative element on the periodic table is fluorine, with a Pauling electronegativity value of 4.0. Although carbon has a slightly higher electronegativity than hydrogen a C-H bond is considered to be non-polar for all practical purposes.
Keywords	dipole moment, polar covalent bond, non-polar bond, electronegativity, Pauling electronegativity scale

01-07-006SumUN

Title	Common Bonding Patterns in Organic Chemistry
Caption	Summary: Common Bonding Patterns in Organic Compounds and Ions
Notes	Summary of the bonding patterns seen in the elements most commonly found in organic compounds. Students should get familiar with all these bonding patterns since they will be seen throughout the whole course.
Keywords	valence electrons, lone pairs, neutral, octet

01-07-009UN

Title	Resonance Forms for the Ion [H2CNH2]+
Caption	Some compoundsÕ structures are not adequately represented by a single Lewis structure. When two or more valence bond structures are possible, differing only in the placement of electrons, the molecule will usually show characteristics of both structures. The different structures are called resonance structures or resonance forms because they are not different compounds, just different ways of drawing the same compound. The actual molecule is said to be a resonance hybrid of its resonance forms. In Solved Problem 1-1(d) we saw that the ion [H2CNH2]1 might be represented by either of the following resonance forms:
Notes	Resonance forms are Lewis structures that can be interconverted by moving electrons only. The true structure will be a hybrid between the contributing resonance forms.
Keywords	resonance structures, resonance forms, resonance hybrid, resonance stabilized, delocalization, charge delocalization

01-07-010UN

Title	Resonance Forms for the Acetate Ion
Caption	For example, the acidity of acetic acid (below) is enhanced by resonance effects. When acetic acid loses a proton, the resulting acetate ion has a negative charge delocalized over both of the oxygen atoms. Each oxygen atom bears half of the negative charge, and this delocalization stabilizes the ion. Each of the carbonÐoxygen bonds is halfway between a single bond and a double bond, and they are said to have a bond order of
Notes	Acetic acid can be deprotonated by water to produce the acetate ion. The acetate ion can be stabilized by resonance. The negative charge is delocalized over the O-C-O atoms in two equivalent resonance forms. The true resonance form is a hybrid between both structures.
Keywords	acetate ion, acetic acid, equilibrium, resonance form, resonance hybrid, delocalized, delocalization

01-07-013UN

Title	Major and Minor Resonance Contributors for Formaldehyde
Caption	Not all resonance forms are equivalent. The major resonance contributor has all octets complete and no charge separation on its atoms. Formaldehyde has two resonance forms, one of them is very polar, with a partial positive charge on carbon and a partial negative charge on oxygen. This structure is a minor resonance form.
Notes	Keep in mind that good resonance forms should have as many octets as possible. Negative charges should be localized on the most electronegative atom present in the molecule. Structures with charge separation are usually minor resonance contributors.
Keywords	octets, resonance, major resonance contributor, minor resonance contributor, charge separation, electronagative

01-07-019T1-2

Title	Condensed Structural Formulas
Caption	TABLE 1-2ÊExamples of Condensed Structural Formulas
Notes	Condensed structural formulas are written without showing all the individual bonds in the molecule. If a group is repeated it may be enclosed in parenthesis and a subscript can specify the times the unit is repeated.
Keywords	Lewis structure, condensed formula

01-07-020T1-3

Title	Condensed Formulas for Double and Triple Bonded Compounds
Caption	TABLE 1-3ÊCondensed Structural Formulas for Double and Triple Bonds
Notes	In condensed formulas double and triple bonds are drawn as they would be in a Lewis structure showing two dashes for a double bond and three dashes for a triple bond
Keywords	double bond, triple bond, condensed formula, Lewis structure

01-07-033T1-4

Title	Line-angle Drawings
Caption	TABLE 1-4ÊExamples of LineÐAngle Drawings
Notes	Line-angle formula (a.k.a. skeletal structure or stick figure) is a shorthand way of drawing organic compounds. Bonds between carbons are represented by lines,. Carbons are present where the line begins and end, and where the lines meet. Nitrogen, oxygen and halogen atoms are shown but hydrogens are not drawn unless they are bonded to a drawn atom.
Keywords	line-angle structure, stick figure, skeletal structure, bond-line structure

01-07-035UN

Title	Dissociation of Acids in Water
Caption	The Arrhenius theory, developed at the end of the nineteenth century, helped to provide a better understanding of acids and bases. Acids were defined as substances that dissociate in water to give H3O1 ions. The stronger acids, such as sulfuric acid (H2SO4), were assumed to dissociate to a greater degree than weaker acids, such as acetic acid (CH3COOH).
Notes	Sulfuric acid (H2SO4) and acetic acid (CH3COOH) dissociate in water to from H3O+ ions. Sulfuric acid, being a strong acid, dissociates to a greater extent than weaker acids such as acetic acid.
Keywords	Arrhenius theory, strong acid, weak acid, hydronium ion, acid dissociation

01-07-037UN

Title	Dissociation of Bases in Water
Caption	Using the Arrhenius definition, bases are substances that dissociate in water to give hydroxide ions. Strong bases, such as NaOH, were assumed to dissociate more completely than weaker, sparingly soluble bases such as Mg(OH)2.
Notes	Arrhenius bases dissolve in water to produce hydroxide ion. Strong bases such as NaOH dissociate to a greater extent in water than weak bases do producing greater amounts of hydroxide.
Keywords	Arrhenius theory, strong base, weak base, hydroxide ion, dissociation

01-07-038UN

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01-07-042T1-5

Title	Relative Strength of Some Common Organic and Inorganic Acids and their Conjugate Bases
Caption	TABLE 1-5ÊRelative Strength of Some Common Organic and Inorganic Acids and Their Conjugate Bases
Notes	Knowing the pKa of some common organic compounds will help in understanding mechanisms in future chapters. The lower the pKa the stronger the acid, the higher the pKa the stronger the conjugate base.
Keywords	acid, conjugate acid, base, conjugate base, strong acid, weak acid, strong base, weak base, acid dissociation constant, base dissociation constant

01-07-052UN

Title	Structural Effects on Acidity
Caption	Electronegativity.Ê A more electronegative element bears a negative charge more easily, giving a more stable conjugate base and a stronger acid. Electronegativities increase from left to right in the periodic table:
Notes	Comparing atom electronegativities is a good way to understand stabilitie of common anions found in organic chemistry, which in turn offers a guide to acidity of compounds. In general highly electronegative atoms make stable anions (conjugate bases) which increases their acidity.
Keywords	electronegative, electron withdrawing, stronger acid, conjugate base

01-07-053UN

Title	Effect of Resonance Stabilization on the Acidic Strength of Some Common Organic Compounds
Caption	Resonance Stabilization.Ê The negative charge of a conjugate base may be delocalized over two or more atoms by resonance. Depending on how electronegative those atoms are, and how many share the charge, resonance delocalization is often the dominant effect in the stabilization of an anion. Consider the following conjugate bases. Ethoxide ion has a negative charge localized on one oxygen atom; acetate ion has the negative charge shared by two oxygen atoms; and the methanesulfonate ion has the negative charge spread over three oxygen atoms. The conjugate acids of these anions show that acids are much stronger if they deprotonate to give resonance-stabilized bases.
Notes	Resonance can contribute to the acidity of a compound. If the negative charge on an atom can be delocalized over two or more atoms, the acidity of that compound will be greater than when the negative charge cannot be delocalized. Thus ethoxide is less acidic than the acetate ion simply because the acetate ion can delocalize the negative charge over the O-C-O atoms (two resonance forms). Methanesulfonic acid can delocalize the charge in three different resonance forms making it more acidic than the acetate ion.
Keywords	resonance, delocalization, electronegativity, acid, conjugate base

01-07-055UN

Title	Bond Formation Between a Nucleophile and an Electrophile
Caption	The Lewis acidÐbase definitions allow reactions having nothing to do with protons to be considered as acidÐbase reactions. Below are some examples of Lewis acidÐbase reactions. Notice that the common Br¿nstedÐLowry acids and bases also fall under the Lewis definition, with a proton serving as the electrophile. Curved arrows are used to show the movement of electrons, generally from the nucleophile to the electrophile.
Notes	To form a bond the electrons of a nucleophile will move toward the electrophile. This movement is shown with a curved arrow. Notice that a nucleophile usually either bears a negative charge, has lone pairs of electrons or both. Electrophiles can bear a positive charge, have an incomplete octet, or can substitute one of its groups for the nucleophile (substitution reaction).
Keywords	nucleophile, electrophile, curved arrow, positive charge, negative charge, substitution reaction

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