Download Chapter 12: Introduction to Organic Chemistry

CHEMISTRY 105
CHAPTER 11: ALKANES
Homework problems: 13, 17, 19, 21, 23, 31, 53, 55
Outline
I.
Studying Organic Chemistry
A. Flash Cards
1. Side A: name of functional group (funct. grp.)
2. Side B: structure of funct. grp.
3. Do cards for nomenclature, structure, new terms
II. New terms for organic molecules VSEPR theory
A. Hybrid orbitals
1. sp3  tetrahedral (109)
2. sp2  trigonal planar (120)
3. sp  linear (180)
III.
Carbon Compounds
A. Carbon Chains
1. normal (n)
2. branched
3. expanded vs. condensed structural formulas
a. expanded shows all bonds
b. condensed omits some bonds – usually CH bonds, sometimes CC
bonds
B. Structural Isomers
1. Same molecular formula
2. Different bonding arrangement
3. Example
a. n-butane vs. isobutane
4. Other types of isomers besides structural
a. conformational
b. stereoisomers
c. others
C. Alkanes
1. Hydrocarbons
a. contain just H and C
b. if all single bonds, then alkane (also called saturated)
c. if at least one double or triple bond, then not alkane (unsaturated)
2. Tetrahedral geometry about each carbon
a. ball and stick models
b. space filling models
3. Chains
a. normal (n) – straight chain compound
b. branched chain
4. Conformational isomers
a. rotation around single bond
b.
and
are conformational isomers
IV.
c. are not structural isomers (have same bonding)
Nomenclature
A. Carbon chain length
1. 1 C = methane
2. 2 C’s = ethane
3. 3 C’s = propane
4. see Table 11.1 p304 for the rest
5. memorize first ten (to decane)
B. Prefix – root – ending
1. Prefix
a. normal or n-  straight chain
b. iso-  usually means methyl branch at second carbon
c. others (sec, tertiary)
2. root
a. from table 10.1, but without –ane ending
b. but-, pent-, etc.
c. assigned to longest chain
3. suffix
a. denotes functional class
b. –ane  saturated or alkane
c. –ene  alkene
d. –yne  alkyne
e. –ol  alcohol
f. only need to know –ane for now
C. Alkyl groups
1. stem plus –yl ending
2. CH3- is methyl
3. CH3CH2- is ethyl
4. Propyl includes
a. n-propyl: CH3CH2CH2b. isopropyl: CH3CHCH3
5. Butyl includes
a. n-butyl
b. sec-butyl
c.
isobutyl
d. tert-butyl
V.
D. Non-alkyl substituents
1. flouro, chloro, bromo, iodo
2. Memorize
E. Naming procedure
1. first, find longest chain
a. this gives root or parent chain
2. look for first point of difference
a. i.e., 1,6,6 trichloroheptane, not 2,2,7
3. number carbons in longest chain
a. number from end which gives lowest total numbers to substituents
b. i.e., prefer 2,2,4 over 2,4,4
4. locate and name alkyl, other substituents
a. include assigned number
b. i.e., 2-methyl
c. i.e., 1-bromo
5. put together substituents and parent chain
a. all one word: 2-methylpropane
b. dashes between number and letters
c. if two or more of same substituent, use di, tri, tetra, penta, etc.
d. i.e., 2,4-dimethylheptane
e. if two or more of different substituents present, order alphabetically
(ignore di, tri, tert, sec)
f. i.e., 1-bromo-2-methylpropane
Cycloalkanes
A. 2n+2 = number of hydrogens on alkane (n = # carbons)
1. If less than 2n+2 H’s, then unsaturated or cyclic
B. Nomenclature
1. prefix cyclo- in front of parent chain
2. substituents numbered around ring
a. such as to give lowest numbers
b. 1,3 not 1,4
3. when two different groups present
a. first alphabetically gets lowest number
b. ignore di, tri, etc.
C. Condensed formulas
1. cyclopropane  triangle
2. cyclobutane  square
3. etc.
D. Shape of cycloalkanes
1. Alkanes
a. free rotation around single bonds
b. 109 angles on each carbon
2. Bond angles of cycloalkanes
a. cyclopropane  60
b. cyclobutane  90
c. these are unstable
d. pentane, butane are slightly bent from planar
e. cyclohexane can have chair or boat form
3. Rotation of cycloalkane bonds
a. no rotation around C-C single bonds
4. Stereoisomers
a. some bonded arrangement (connectivity)
b. different spatial arrangement
c. test – can you pick it up and put it down on top of the other
5. Cis-trans
a. cis same side
b. trans: opposite sides
D. Boat vs Chair
1. axial vs equitorial
VI.
Physical and Chemical Properties
A. Homologous series
1. insert one more -CH2B. Melting point and boiling point
1. 1-4 C’s: gases
2. 5-20 C’s: liquids
3. 21+ C’s: waxy solids
4. low intermolecular attractions
C. Hydrophobic/hydrophilic
1. alkanes are insoluble in water
2. some functional groups are soluble in water
D. Reactivity
1. alkanes are least reactive of organic compounds
2. unaffected by acids/bases
3. cannot be reduced
4. sometimes called parafins
a. latin for little affinity
b. parafin wax on milk cartons, etc
5. can be halogenated
6. can be oxidized
a. burning produces gases, heat
b. incomplete combustion may result in C, CO
Chapter Objectives
Knowledge
Memorize the stem for the first ten carbons in Table 11.1, p304
Memorize the four common halide substituents
Recall definitions for n-, iso-, and t-butyl as it applies to nomenclature
Comprehension
Be able to pick out the longest chain in a carbon structure
Understand the difference between conformers, structural isomers, and stereoisomers
Understand how the difference in intermolecular forces give organic compounds vastly
different properties than organic compounds
Differentiate between a condensed formula and an expanded formula
Differentiate between saturated (all alkane) and unsaturated (alkenes/alkynes)
Recognize and be able to make simple compounds from/with ball and stick models
Recognize the bond angle (109) and free rotation around an sp3 bond
Determine products of oxidation and incomplete oxidation of hydrocarbons
Application
Apply nomenclature system (prefix-stem-suffix) to name alkane chains up to 10 carbons
Determine whether a carbon bond is sp, sp2, or sp3 (bond hybridization)
Determine whether the shape of the arrangement of atoms around a carbon is tetrahedral,
trigonal planer, or linear
Write a condensed structural formula from an expanded one and vice-versa
Identify structures as conformational “isomers” (the same molecule), structural isomers
(same atoms but different connectivity) or stereoisomers (same atoms and
connectivity, yet not identical – cis and trans are only examples of this so far)
Analysis
Determine structure from IUPAC and common names used in this chapter
Name branched chain compounds of 10 carbons or less with several substituents