Download CHEMISTRY 105

CHEMISTRY 105
CHAPTER 11: ORGANIC COMPOUNDS: ALKANES
Homework problems: 4, 8, 14, 18, 22, 28, 36, 50, 52, 60
Outline
I.
II.
III.
IV.
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
Early Organic Chemistry
A. Vital Force in living beings
B. Organic compounds could not be made without vital force
C. In 1828, a German synthesized an organic cmpd from an inorganic
1. ammonium cyanate  urea
2. so much for the “vital force” theories
Organic or Inorganic
A. Inorganic
1. Ionic bonds
a. limits the size and number of different atoms in compound
b. high intermolecular forces
c. large agglomerations of molecules in ionic lattice
d. roughly 250,000 different structures identified
e. includes CO, CO2, carbonates (XCO3), and cyanates (XCN)
f. X is (are) cation(s)
B. Organic
1. Covalent bonds
a. a. can be all sizes, including very large
b. low intermolecular forces
c. high intramolecular forces
d. more than 6,000,000 organic compounds identified
2. Hybrid orbitals
a. sp3  tetrahedral (109.5)
b. sp2  trigonal planar (120)
c. sp  linear (180)
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 relationships besides structural isomers
a. conformers
b. stereoisomers
c. not related
C. Functional Groups
1. Table 11.2, p348 lists some common funct. grps
a. memorize first ten (up to and including -COOH)
2. Funct. grps. Are a particular arrangement of atoms
3. May include N, O, S, or others as well as C and H
4. Different funct. grps. dictate a lot of the properties of the molecule
D. 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
V.
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 11.4 p356 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 11.4, 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
D. Non-alkyl substituents
1. Table 11.6 p. 358
2. Memorize list
E. Naming procedure
1. first, find longest chain
a. this gives root or parent chain
Examining the three line structures above tells us that they are all the same molecule.
However, not all carbon chains are equally long. In the first and second structures, the
red chains are both four C’s long. In the third structure, the red chain is 5 C’s long. The
longest chain isn’t always left to right. It just happened that way here. But it is necessary
to find the longest carbon chain first. The name of this parent chain will be pentane (3methylpentane, to give the full name), not butane (not 2-ethylbutane).
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
examples:
Br
Cl
3-ethylpentane
Cl
2-bromo-3,3-dichlorohexane
4-ethyloctane
3-methylheptane
I
NO2
1-iodo-2-nitrobutane
I
4-iodo-2,2-methylhexane
Cl
3-methylpentane
2-chloro-3-ethylpentane
Cl
Cl
Br
2-bromo-1,2-chloropropane
O2N
4-iodo-5-methyl-1-nitrohexane
I
3,4-diethyl-1-nitroheptane
NO2
VI.
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.
methylcyclohexane (1 substituent, no number necessary)
Both of these are trans 1,2-dimethyl cyclohexane. The drawing on the left is how the
book does it. Imagine the not quite flat cyclohexane ring as a lumpy pancake and you are
looking at an edge view. Because the front edge is coming towards you, those three
carbons are drawn with wedges. Off the ring are two methyl groups on adjacent ring
carbons. One is pointing up and one is pointing down. They are trans to each other. I
find it easier to draw the same molecule as on the right. Imagine you are looking down at
the top (or up to the bottom) of that same cyclohexane ring. One methyl is coming
towards you (wedge) and one going away (dash). This structure is also trans
These are both cis 1,2-cyclohexane. In the drawing on the left, the two methyls are both
coming towards you (are on the same side of the ring), and on the right, the two methyls
are pointed away from you (but are still on the same side of the ring as each other).
VII.
D. Shape of cycloalkanes
1. Alkanes
a. free rotation around single bonds
b. 109.5 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
Properties
A. Homologous series
1. insert one more -CH2-
B. 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 first ten functional groups in Table 11.2, p 348
Memorize the stem for the first ten carbons in Table 11.4, p356
Memorize the six common non-alkyl substituent group names (Table 11.6, p358)
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
Identify common substituents, such as those found in Tables 11.5 and 11.6
Understand the difference between conformers, structural isomers, and stereoisomers
Understand how the difference in intermolecular forces give organic compounds vastly
different properties than inorganic 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