Unlike alkenes and alkynes each pair of electrons does not sit between two

Unlike alkenes and alkynes each pair of electrons

This preview shows page 88 - 104 out of 144 pages.

Unlike alkenes and alkynes, each pair of -electrons does not sit between two atoms. Rather, the electrons are delocalized . 88
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Bonding in Benzene The 6 delocalized electrons in the bond are shared equally by all 6 carbon atoms. Resonance delocalizes the shared pairs of electrons of the C-C π-bonds. 89
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What is the molecular formula of naphthalene? A. C 10 H 6 B. C 10 H 8 C. C 10 H 10 D. C 10 H 12 ConcepTest 1.4.A Organic Chemistry, Learning Objective 1
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According to the single Lewis structure shown above ( ignoring resonance ), what orbitals overlap to form bond b ? A. C(sp 3 ) with C(sp 3 ) bond B. C(sp 2 ) with C(sp 2 ) bond C. C(sp 2 ) with C(sp 2 ) bond D. C(sp 2 ) with C(sp 2 ) bond & C(2p) with C(2p) bond ConcepTest 1.4.B.i Organic Chemistry, Learning Objective 1
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A. 1 B. 1.5 C. 2 D. 2.5 ConcepTest 1.4.B.ii Organic Chemistry, Learning Objective 1 Considering resonance , what is the order of bond b ?
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Stabilization of -Electrons by Delocalization 93 Addition of hydrogen to cyclohexene releases 120 kJ/mol.. Enthalpy, H −120 kJ/mol
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Stabilization of -Electrons by Delocalization 94 Addition of hydrogen to cyclohexene releases 120 kJ/mol. If this is the energy cost of introducing one double bond into a six-carbon ring, we would expect cyclohexadiene to release 240 kJ/mol/ Enthalpy, H −120 kJ/mol −232 kJ/mol
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Stabilization of -Electrons by Delocalization 95 Addition of hydrogen to cyclohexene releases 120 kJ/mol. If this is the energy cost of introducing one double bond into a six-carbon ring, we would expect cyclohexadiene to release 240 kJ/mol, and cyclohexatriene to release 360 kJ/mol. Enthalpy, H −120 kJ/mol −232 kJ/mol −360 kJ/mol expected if 3 C=C bonds protonated −208 kJ/mol Benzene is 152 kJ/mol more stable than expected!
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Summary of Student Skills 96 L.O.1.2.c. Draw and interpret the different representations of benzene. L.O.1.2.d. Apply knowledge of bond properties (length, strength, bond order) to observed physical and thermochemical properties.
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CHEM 104 Whole Class 97 Module 1: Organic Chemistry Functional Groups: Ethers and Alcohols
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Organic Functional Groups Functional Group : Groups of atoms and bonds that are responsible for the characteristic chemical reactions of molecules. The same functional group will undergo the same or similar chemical reaction(s) regardless of the size of the molecule it is a part of. R and R’s: other unspecified organic molecule fragments
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Functional Groups Encountered So Far: 99
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Alcohols and Ethers Ethers: Quite unreactive, and therefore are good solvents for molecules with similar intermolecular forces. 100
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“Sweet Oil of Vitriol” 101
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Alcohols and Ethers Alcohols: Contain one or more hydroxyl group , –OH. Named from the parent hydrocarbon; suffix is changed to -ol and a number designates the carbon to which the hydroxyl group is attached. 102
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Ethanol and dimethyl ether are structural isomers with the molecular formula C 2 H 6 O.
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