1. Chemistry 121 Winter 17
Introduction to Organic Chemistry and Biochemistry
Instructor Dr. Upali Siriwardane (Ph.D. Ohio State)
Office: 311 Carson Taylor Hall ; Phone: ;
Contact me trough if you have questions
Online Tests on Following days
December 16, 2016: Test 1 (Chapters 12-13)
January 23, 2017 : Test 2 (Chapters 14-16)
February 10, 2017 : Test 3 (Chapters 17-19)
February 22, 2017 : Test 4 (Chapters 20-22)
February 23, 2017: Make Up Exam: Chapters 12-22)

2. GHW Questions
GHW#2
CHEM 121 Winter 16

3. Chapter 12. Saturated Hydrocarbons
12.1 Organic and Inorganic Compounds, 341
12.2 Bonding Characteristics of the Carbon Atom, 342
12.3 Hydrocarbons and Hydrocarbon Derivatives, 342
12.4 Alkanes: Acyclic Saturated Hydrocarbons, 343
12.5 Structural Formulas, 344
12.6 Alkane Isomerism, 346
12.7 Conformations of Alkanes, 348
12.8 IUPAC Nomenclature for Alkanes, 350
12.9 Line-Angle Structural Formulas for Alkanes, 356
12.10 Classification of Carbon Atoms, 358
12.11 Branched-Chain Alkyl Groups, 359
12.12 Cycloalkanes, 361
12.13 IUPAC Nomenclature for Cycloalkanes, 362
12.14 Isomerism in Cycloalkanes, 363
12.15 Sources of Alkanes and Cycloalkanes, 365
12.16 Physical Properties of Alkanes and Cycloalkanes, 367
12.17 Chemical Properties of Alkanes and Cycloalkanes, 368
12.18 Halogenated Alkanes and Cycloalkanes, 371
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4. Isomerism in Organic Molecules
Isomers - different compounds having the same molecular formula but different structural formulas
There are two type of Isomers:
Constitutional isomerism: Different connections among atoms in the
Skeleton
Position
Functional group
Stereoisomerism: Same connectivity among atoms, but these atoms differ in spatial orientation
geometric
conformational
optical
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5. Constitutional Isomers
Skeletal (Chp. 12)
Functional (Chp. 14)
Positional (Chp. 12)
Stereoisomers
Conformational (Chp.12)
Geometric (Chp. 13)
Enantiomers (Optical) (Chp. 16)
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6. Constitutional isomers in butane
Constitutional isomers: compounds with the same molecular formula but a different connectivity of their atoms in the skeleton.
There are two constitutional isomers with molecular formula C4H10
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7. Constitutional Isomers of Alkanes (CnH2n+2)
Number n of carbon Atoms
Isomers of CnH2n+2 1 2 3 4 5 6 7 9 8 18 35 10 75 11
159 12
355 13
802
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8. 1. Give the number of constitutional isomers possible in following alkanes.
a) CH _________ b) C2H _________
c) C3H _________ d) C4H _________ e) C5H _________ f) C6H _________
g) C7H _________ h) C8H _________
i) C9H _________
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9. a) Expanded condensed formula: b) Line-angle formula:
2. Give the IUPAC name of the following branched alkane: CH3C(CH3)2CH2CH(CH2CH3)CH2CH3
a) Expanded condensed formula:
b) Line-angle formula:
c) Branched Alkyl groups and their names:
d) IUPAC name of the compound:
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10. Types of carbon atoms
Carbon atoms in alkanes and other organic compounds are classified by the number of other carbons directly bonded to them.
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11. Types of carbon atoms
1. Primary (1◦) Carbon connected to one carbon atoms.
2. Secondary (2◦) Carbon connected to two carbon atoms.
3. Tertiary (3◦) Carbon connected to three carbon atoms.
4. How many primary, secondary, and tertiary carbons in the
two different structures of C4H10
Primary =
Secondary =
Tertiary =
Primary =
Secondary =
Tertiary =
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12. Identify the type of carbon atoms in the following structure
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13. GHW#1: #9 IUPAC name of the following branched alkane:
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14. Reactions of alkanes Combustion
CH4(g) + 2O2(g) CO2(g) + 2H2O(g)
Many alkanes are used this way - as fuels
Methane - natural gas
Propane - used in gas grills
Butane - lighters
Gasoline - mixture of many hydrocarbons,
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15. Reactions of alkanes Halogenation CH4(g) + Cl2(g) CH3Cl(g) + HCl(g)
A reaction where a halogen replaces one or more hydrogens.
CH4(g) + Cl2(g) CH3Cl(g) + HCl(g)
Used to prepare many solvents
Dichloromethane, methylene chloride- paint stripper
Trichloromethane, Chloroform (CHCl3)- once used as anesthesia
1,2-dichloroethane - dry cleaning fluid
heat or light
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16. 4. Complete combustion reaction of following alkanes. a) CH4 b) C4H10
c) C5H12
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17. Cycloalknes Cyclic alkanes: General molecular formula, CnH2n
Structure and nomenclature
named similar to noncyclic alkanes
to name, prefix the name of the corresponding open-chain alkane with cyclo-, and name each substituent on the ring
if only one substituent, no need to give it a number
if two substituents, number from the substituent of lower alphabetical order
if three or more substituents, number to give them the lowest set of numbers, and then list substituents in alphabetical order
in planar cyclopentane, all C-C-C bond angles are 108°, which differ only slightly from the tetrahedral angle of 109.5°consequently there is little angle strain
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18. Cycloalkanes :saturated hydrocarbons with a carbon ring
Have C-C single bonds in a ring structure.
General formula CnH2n
cyclobutane
cyclopropane
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19. Naming Cycloalkanes
Have the carbons connected in a ring. These compounds are known collectively as
To name a cycloalkane, use the prefix cyclo- with the parent. If there is only one substituent, a number is not needed.
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20. Cycloalkanes
Cycloalkanes have molecular formula CnH2n and contain carbon atoms arranged in a ring. Simple cycloalkanes are named by adding the prefix cyclo- to the name of the acyclic alkane having the same number of carbons.
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21. Naming simple of cycloalkanes:
cyclopropane
cyclobutane
cyclopentane
cyclohexane
cycloheptane
cyclooctane
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22. Ring strain in cycloalkane
The stability of cycloalkanes depends on their ability to relieve ring strain when the bond angles are less than 109.5˚.
Most stable
Least stable
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23. Naming branched cycloalkanes
Commonly written as line-angle formulas
examples:
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24. IUPAC name of the following substituted cycloakane
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25. Cis and trans Geometrical isomers of Cycloalkanes
two groups are said to be located cis to each other if they lie on the same side of a plane.
If they are on opposite sides, their relative position is described as trans.
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26. Disubstituted Cycloalkanes
There are two different 1,2-dimethylcyclopentanes—one having two CH3 groups on the same side of the ring and one having them on opposite sides of the ring.
A and B are isomers. Specifically, they are stereoisomers.
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27. Haloalkanes
An alkane in which one or more H atoms is replaced with a halogen (F, Cl, Br, or I)
CH3Br 1-bromomethane
Br (methyl bromide)
CH3CH2CHCH3 2-bromobutane Cl
chlorocyclobutane
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28. _________________ _________________ b) CHCl3 c) CCl3F e) CCl2F2
6. Give the common/IUPAC names of following substituted alkanes: Common IUPAC
a) CH2Cl2
_________________ _________________
b) CHCl3
c) CCl3F
e) CCl2F2
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29. _________________ _________________ b) CHCl3 c) CCl3F e) CCl2F2
6. Give the common/IUPAC names of following substituted alkanes: Common IUPAC
a) CH2Cl2
_________________ _________________
b) CHCl3
c) CCl3F
e) CCl2F2
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30. 7. Define following types of terms used in describing isomerism:
a) Isomers: An example:
b) Constitutional isomers:
An example:
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31. Conformers of Alkanes
Structures resulting from the free rotation of a C-C single bond
May differ in energy. The lowest-energy conformer is most prevalent.
Molecules constantly rotate through all the possible conformations.
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32. Ethane Conformers Staggered conformer has lowest energy.
Dihedral angle = 60 degrees H
Newman
projection
Ball & Stick model
Dihedral angle H
sawhorse H H H H H
Staggered Conformation
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33. Ethane Conformers (2) Eclipsed conformer has highest energy
Dihedral angle = 0 degrees
=>
Eclipsed
Eclipsed
Staggered
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34. Conformational Analysis
Torsional strain: resistance to rotation.
For ethane, only 12.6 kJ/mol
=>
eclipsed
staggered
eclipsed
staggered
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35. Conformational Analysis Butane
anti
gauche
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36. Conformational Analysis Butane
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37. Stereoisomers c) Conformational stereroisomers:
d) Geometric stereoisomers:
e) Optical stereoisomers (d and l Enantiomers):
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38. Geometrical Isomers
There are two different 1,2-dimethylcyclopentanes—one having two CH3 groups on the same side of the ring (or double bond) and one having them on opposite sides of the ring (or double bond) .
A and B are isomers. Specifically, they are stereoisomers.
CHEM 121 Winter 16

39. Optical Isomers-Enantiomers
Dextrorotation and levorotation (refer to the properties of rotating plane polarized light.
If the light rotates clockwise (d) as it approaches an observer or light with a anticlockwise
rotation (l)
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40. 8) Describe the conformational isomerism in following alkanes:
a) Butane, C4H10:
b) Cyclopenatane, C5H10:
c) Cyclohexane C6H12:
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41. Units of Unsaturation
Units of Unsaturation is the number of double (p) bonds and/or rings in the molecule.
Each ring or multiple bond replaces 2 H's in the alkane formula CnH2n+2
It relates molecular formula to possible structures
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42. 9. Calculate the units of unsaturation in following hydrocarbons
a) Butane, C4H10:
b) Cyclopenatane, C5H10:
c) Ethene (ethylene), C2H4:
d) Cyclohexa-1,3,5-triene (Benzene), C6H6:
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43. Chemical Reactivity of Cycloalkanes
Ring strain in cyclopropane and cyclobutane cause them to under go
addition reaction like double bond
Cycloalkanes with C >4 reacts like akanes undergoing combustion and halogenation
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