有机化学英文课件cha
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有机化学英文原版ppt
Number of Covalent Bonds to an Atom Atoms with one, two, or three valence electrons form one, two, or three bonds Atoms with four or more valence electrons form as many bonds as they need electrons to fill the s and p levels of their valence shells to reach a stable octet
1.1 Atomic Structure
Structure of an atom
Positively charged nucleus (very dense, protons and neutrons) and smal (10-15 m) Negatively charged electrons are in a cloud (10-10 m) around nucleus Diameter is about 2 × 10-10 m (200 picometers (pm)) [the unit angstrom (Å) is 10-10 m = 100 pm]
1.5 The Nature of the Chemical Bond
Atoms form bonds because the compound that results is more stable than the separate atoms Ionic bonds in salts form as a result of electron transfers Organic compounds have covalent bonds from sharing electrons (G. N. Lewis, 1916) Lewis structures shown valence electrons of an atom as dots Hydrogen has one dot, representing its 1s electron Carbon has four dots (2s2 2p2) Stable molecule results at completed shell, octet (eight dots) for main-group atoms (two for hydrogen)
有机化学英文课件chapter3
Stereoisomerism and Chirality
Macintosh PICT Macintosh PICT im age form at im age form at is not supported is not supported
Chapter 3
3-2
Isomers
Isomers: different compounds with the same molecular formula
M a c in to s h P IC T im a g e fo r m a t
is n o t s u p p o r te d
3-13
R,S Convention
3. Atoms participating in a double or triple bond are considered to be bonded to an equivalent number of similar atoms by single bonds
• an achiral object has at least one element of symmetry • plane of symmetry: an imaginary plane passing
through an object dividing it so that one half is the mirror image of the other half • center of symmetry: a point so situated that identical components are located on opposite sides and equidistant from that point along the axis passing through it
有机化学英文课件chpt9_3
CH3CH3 CH2 CHCH3 pKa ~ 50 CH3SO2CH3 29 40
(C6H5)2CH2 32.3 H H 16.6
CH3CN 31.3 CH3NO2 17.21
C6H5COCH3 24.7
酮式和烯醇式—— 互变异构
O CH3 C CH3 H or OH
+
OH CH3 C CH2
Organic Chemistry Organic Chemistry Xiamen University Xiamen University
PhCH CH C H
Organic Chemistry Organic Chemistry Xiamen University Xiamen University
(4) 定向缩合
交叉羟醛缩合时需要解决的2个问题:
2个含α−H的醛酮进行交叉缩合 哪个出 α−C 哪个出羰基 不对称的酮进行交叉缩合时 提供哪一 侧的α−C参与反应
反应机理:
O CH3 C H O CH3 C H OH O CH2 C H O CH3 C H O H2 O O CH2 C H OH CH3 C H O
CH2 C H
CH2 C H
Organic Chemistry Organic Chemistry Xiamen University Xiamen University
O
R C
CH2 O
Organic Chemistry Organic Chemistry
O
Xiamen University Xiamen University
Organic Chemistry Organic Chemistry Xiamen University Xiamen University
有机化学英文课件chapter5
is n o t s u p p o rte d
5-15
The E,Z System
Example: name each alkene and specify its configuration by the E,Z system
M acintosh P IC T im age form at
• it takes approximately 264 kJ (63 kcal)/mol to break the pi bond in ethylene; that is, to rotate one carbon by 90° with respect to the other so that there is no overlap between 2p orbitals on adjacent carbons
conditions we describe in Ch 6-20
5-4
Structure of Alkenes
A double bond consists of
• one sigma bond formed by the overlap of sp2 hybrid orbitals and one pi bond formed by the overlap of parallel 2p orbitals
Organic Chemistry
William H. Brown Christopher S. Foote Brent L. Iverson
5-1
M acintosh P IC T im age form at
is n o t s u pAplkoernteesd:
Structure and Nomenclature
5-15
The E,Z System
Example: name each alkene and specify its configuration by the E,Z system
M acintosh P IC T im age form at
• it takes approximately 264 kJ (63 kcal)/mol to break the pi bond in ethylene; that is, to rotate one carbon by 90° with respect to the other so that there is no overlap between 2p orbitals on adjacent carbons
conditions we describe in Ch 6-20
5-4
Structure of Alkenes
A double bond consists of
• one sigma bond formed by the overlap of sp2 hybrid orbitals and one pi bond formed by the overlap of parallel 2p orbitals
Organic Chemistry
William H. Brown Christopher S. Foote Brent L. Iverson
5-1
M acintosh P IC T im age form at
is n o t s u pAplkoernteesd:
Structure and Nomenclature
有机化学英文课件chapter8共52页
u All liquid bromoalkanes and iodoalkanes are more dense than water
u Di- and polyhalogenated alkanes are more dense than water
M a c in to s h P IC T im a g e fo rm a t
u van der Waals forces: a group intermolecular attractive forces including
• dipole-dipole forces • dipole-induced dipole forces • induced dipole-induced dipole (dispersion) forces
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o rte d
8-9
Boiling Points
u For an alkane and a haloalkane of comparable size and shape, the haloalkane has the higher boiling point
u Common names: name the alkyl group followed by the name of the halide
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o r te d
8-5
Nomenclature
u van der Waals forces pull molecules together
u Di- and polyhalogenated alkanes are more dense than water
M a c in to s h P IC T im a g e fo rm a t
u van der Waals forces: a group intermolecular attractive forces including
• dipole-dipole forces • dipole-induced dipole forces • induced dipole-induced dipole (dispersion) forces
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o rte d
8-9
Boiling Points
u For an alkane and a haloalkane of comparable size and shape, the haloalkane has the higher boiling point
u Common names: name the alkyl group followed by the name of the halide
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o r te d
8-5
Nomenclature
u van der Waals forces pull molecules together
有机化学英文课件chapter1
1-13
Formation of Ions
A rough guideline:
• ions will form if the difference in electronegativity between interacting atoms is 1.9 or greater
• example: sodium (EN 0.9) and fluorine (EN 4.0)
• about 1000 new ones are identified each day!
C is a small atom
• it forms single, double, and triple bonds • it is intermediate in electronegativity (2.5) • it forms strong bonds with C, H, O, N, and some metals
Although all covalent bonds involve sharing of electrons, they differ widely in the degree of sharing
We divide covalent bonds into
• nonpolar covalent bonds • polar covalent bonds
• in forming Na+F-, the single 3s electron from Na is transferred to the partially filled valence shell of F
M
a c in t o sis
not
su p p
P
Formation of Ions
A rough guideline:
• ions will form if the difference in electronegativity between interacting atoms is 1.9 or greater
• example: sodium (EN 0.9) and fluorine (EN 4.0)
• about 1000 new ones are identified each day!
C is a small atom
• it forms single, double, and triple bonds • it is intermediate in electronegativity (2.5) • it forms strong bonds with C, H, O, N, and some metals
Although all covalent bonds involve sharing of electrons, they differ widely in the degree of sharing
We divide covalent bonds into
• nonpolar covalent bonds • polar covalent bonds
• in forming Na+F-, the single 3s electron from Na is transferred to the partially filled valence shell of F
M
a c in t o sis
not
su p p
P
有机化学 英文课件 chapter(5)
• acid: a substance that produces H3O+ ions aqueous solution • base: a substance that produces OH- ions in aqueous solution • this definition of an acid is a slight modification of the original Arrhenius definition, which was that an acid produces H+ in aqueous solution • today we know that H+ reacts immediately with a water molecule to give a hydronium ion
Organic Chemistry
William H. Brown Christopher S. Foote Brent L. Iverson
4-1
Acids and Bases
Chapter 4
4-2
Arrhenius Acids and Bases
In
1884, Svante Arrhenius proposed these definitions
Conjugate Acids & Bases
for
protonation on the carbonyl oxygen, we can write three contributing structures two place the positive charge on oxygen, one places it on carbon
+
Organic Chemistry
William H. Brown Christopher S. Foote Brent L. Iverson
4-1
Acids and Bases
Chapter 4
4-2
Arrhenius Acids and Bases
In
1884, Svante Arrhenius proposed these definitions
Conjugate Acids & Bases
for
protonation on the carbonyl oxygen, we can write three contributing structures two place the positive charge on oxygen, one places it on carbon
+
有机化学英文课件chapter4
Many organic molecules have two or more sites that can act as proton acceptors
in this chapter, we limit our discussion to carboxylic acids, esters, and amides in these molecules, the favored site of protonation is the one in which the charge is more delocalized question: which oxygen of a carboxylic acid is protonated?
Consider the reaction between acetic acid and sodium bicarbonate
we can write the equilibrium as a net ionic equation we omit Na+ because it does not undergo any chemical change in the reaction
the pi electrons of 2-butene, for example, react with HBr by proton transfer to form a new C-H bond
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o rte d
the result is formation of a carbocation, a species in which one of its carbons has only six electrons in its valence shell and carries a charge of +1
in this chapter, we limit our discussion to carboxylic acids, esters, and amides in these molecules, the favored site of protonation is the one in which the charge is more delocalized question: which oxygen of a carboxylic acid is protonated?
Consider the reaction between acetic acid and sodium bicarbonate
we can write the equilibrium as a net ionic equation we omit Na+ because it does not undergo any chemical change in the reaction
the pi electrons of 2-butene, for example, react with HBr by proton transfer to form a new C-H bond
M a c in to s h P IC T im a g e fo rm a t
is n o t s u p p o rte d
the result is formation of a carbocation, a species in which one of its carbons has only six electrons in its valence shell and carries a charge of +1
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• Some nucleophilic substitution reactions
Solvents
• Protic solvent: a solvent that is a hydrogen bond donor – the most common protic solvents contain -OH groups
Protic Solvents
Aprotic Solvents
Mechanisms
• Chemists propose two limiting mechanisms for nucleophilic substitution – a fundamental difference between them is the timing of bond-breaking and bond-forming steps
Organic Chemistry
William H. Brown Christopher S. Foote Brent L. Iverson
Nucleophilic Substitution and
-Elimination
Chapter 9
Nucleophilic Substitution
• Nucleophilic substitution: any reaction in which one nucleophile substitutes for another at a tetravalent carbon
• At one extreme, the two processes take place simultaneously; designated SN2 – S = substitution – N = nucleophilic – 2 = bimolecular (two species are involved in the rate-determining step)
• This mechanism is designated SN1 where – S = substitution – N = nucleophilic – 1 = unimolecular (only one species is involved in the rate-determining step)
Dielectric Constant
• Solvents are classified as polar and nonpolar – the most common measure of solvent polarity is dielectric constant
• Dielectric constant: a measure of a solvent’s ability to insulate opposite charges from one another – the greater the value of the dielectric constant of a solvent, the smaller the interaction between ions of opposite charge dissolved in that solvent – polar solvent: dielectric constant > 15 – nonpolar solvent: dielectric constant < 15
• Aprotic solvent: a solvent that cannot serve as a hydrogen bond donor – nowhere in the molecule is there a hydrogen bonded to an atom of high electronegativity
– Step 3: proton transfer completes the reaction
Mechanism - SN1
Evidence of SN reactions
1. What is relationship between the rate of an SN reaction and: – the structure of Nu? – the structure of RLv? – the structure of the leaving group? – the solvent?
Mechanism - SN1
– Step 1: ionization of the C-X bond gives a carbocation intermediate
Mechanism - SN1
– Step 2: reaction of the carbocation (an electrophile) with methanol (a nucleophile) gives an oxonium ion
• Nucleophile: a molecule or ion that donates a pair of electrons to another molecule or ion to form a new covalent bond; a Lewis base
Nucleophilic Substitution
Mechanism - SN2
– botransition state of the rate-determining step
Mechanism - SN2
Mechanism - SN1
• Bond breaking between carbon and the leaving group is entirely completed before bond forming with the nucleophile begins
2. What is the stereochemical outcome if the leaving group is displaced from a chiral center?
Solvents
• Protic solvent: a solvent that is a hydrogen bond donor – the most common protic solvents contain -OH groups
Protic Solvents
Aprotic Solvents
Mechanisms
• Chemists propose two limiting mechanisms for nucleophilic substitution – a fundamental difference between them is the timing of bond-breaking and bond-forming steps
Organic Chemistry
William H. Brown Christopher S. Foote Brent L. Iverson
Nucleophilic Substitution and
-Elimination
Chapter 9
Nucleophilic Substitution
• Nucleophilic substitution: any reaction in which one nucleophile substitutes for another at a tetravalent carbon
• At one extreme, the two processes take place simultaneously; designated SN2 – S = substitution – N = nucleophilic – 2 = bimolecular (two species are involved in the rate-determining step)
• This mechanism is designated SN1 where – S = substitution – N = nucleophilic – 1 = unimolecular (only one species is involved in the rate-determining step)
Dielectric Constant
• Solvents are classified as polar and nonpolar – the most common measure of solvent polarity is dielectric constant
• Dielectric constant: a measure of a solvent’s ability to insulate opposite charges from one another – the greater the value of the dielectric constant of a solvent, the smaller the interaction between ions of opposite charge dissolved in that solvent – polar solvent: dielectric constant > 15 – nonpolar solvent: dielectric constant < 15
• Aprotic solvent: a solvent that cannot serve as a hydrogen bond donor – nowhere in the molecule is there a hydrogen bonded to an atom of high electronegativity
– Step 3: proton transfer completes the reaction
Mechanism - SN1
Evidence of SN reactions
1. What is relationship between the rate of an SN reaction and: – the structure of Nu? – the structure of RLv? – the structure of the leaving group? – the solvent?
Mechanism - SN1
– Step 1: ionization of the C-X bond gives a carbocation intermediate
Mechanism - SN1
– Step 2: reaction of the carbocation (an electrophile) with methanol (a nucleophile) gives an oxonium ion
• Nucleophile: a molecule or ion that donates a pair of electrons to another molecule or ion to form a new covalent bond; a Lewis base
Nucleophilic Substitution
Mechanism - SN2
– botransition state of the rate-determining step
Mechanism - SN2
Mechanism - SN1
• Bond breaking between carbon and the leaving group is entirely completed before bond forming with the nucleophile begins
2. What is the stereochemical outcome if the leaving group is displaced from a chiral center?