CHEM 30B  Dr. R. Rinehart      Chapter 11  ALKANES  

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See the learning objectives

A set of 66 "lecture overheads" for much of this chapter
by Warren Gallagher at the University of Wisconsin, Eau Claire
http://www.chem.uwec.edu/Chem150_S06/Pages/Lecture-slides/C150_lect01_slides.html 
printable for handout at
 http://www.chem.uwec.edu/Chem150_S06/Pages/Lectnotes/C150_lect01_print.pdf

I. The nature of “Organic” Chemistry
A.    
Inorganic C:   CO, CO2,  (HCO3-, CO3-2),  CN-,  OCN-,  SCN-,  C-4  

Click to see Chime structures of:   graphite    diamond    fullerene [buckyball]

B. Organic C: originally believed to  necessarily originate from (once-)LIVING sources  BUT, Wohler (1828) converted ammonium cyanate  NH4OCN  to  urea  H2NCONH2  by heating, forcing a total rethinking of the concept. NOW, organic chemistry  is defined as the branch of chemistry dealing with all compounds of carbon except  those listed above.  

            C. Organic vs. Inorganic Compounds   
                       
Inorganic: 2.5x105 known;  Organic: >6x106 known.   
   
                                 Q. Why the big difference??

  II. It’s the BONDING, folks!  

For a really good tutorial on chemical bonding in organic molecules that will also be very useful in Chapter 12, go to:  
http://www.chem.ox.ac.uk/vrchemistry/orbitals/html/page01.htm 

close the new window when you are finished

A. Covalent bonds: shared electron pairs

Common patterns of covalent bonding

B. . Hybrid orbitals: 6C  1s22s22p2 ;   {2s+2px+2py+2pz} form 4 equivalent sp3 orbitals

If you're using either Netscape or Internet Explorer, AND have Macromedia's Shockwave download,    
             Colby College's Hybrid Orbital tutorial.   
http://www.colby.edu/chemistry/OChem/DEMOS/Orbitals.html 
               Raymond Chang's Hybrid Orbital Flash Movies  
                                         http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/hybrv18.swf  
  
            Atomic Orbitals at Purdue University  
 http://www.chem.purdue.edu/gchelp/aos/index.html  

C.    Bond geometry: sp3 hybridization shows tetrahedral geometry

D.    Chains of carbons with multiple possible arrangements  [S&S table 1.5, p. 13]  

            E. Hydrocarbons: just with C and H alone, >106 possible compounds .
                        Five major classes of hydrocarbons listed below:

                        1. ALKANES                           CnH2n+2          “RH” 
                       
2.
CYCLOALKANES              CnH2n 
                       
3.
Alkenes:                         contain C=C double bonds   CnH2n 
                       
      4. Alkynes:                         Contain CC triple bonds     CnH2n-2   
                       
5.
Aromatics:     e.g. benzene, C6H6 :  cyclic, “conjugated” systems  ’nuff said for now!   

Hydrocarbons by Charles Ophardt at Elmhurst College, IL
http://www.elmhurst.edu/~chm/vchembook/500hydrocarbons.html
see his additional related pages from the links on the page above

III. Types of Chemical FORMULAS we’ll be using 

A.  Empirical: relative atomic ratios; result of elemental analysis
B.  MOLECULAR
: actual numbers of each type of atom e.g. glucose C6H12O6  
C.  STRUCTURAL
: show how the atoms are arranged and connected together.    
   
         1.      Lewis structures:  yes,  they’re baaaack!  
            2.     
Kekule structures:  a short line indicates each covalent bond  [we’ll use them a lot]
                             Each atom is shown. 
           
3.  Condensed:  hexane, C6H12 is CH3(CH2)4CH3 
   
         
             easily incorporated into text;  
           
4.  Skeletal or bond-line:  
   
                         H usually omitted when attached to C [exception: aldehyde], 
                                    H is generally shown when attached to heteroatoms like O or N;
 
                           
lines used to indicate C-C and C-E bonds, 
                               
where E = any element other than C or H
   
                         symbol for C usually omitted  
                                   
[end of line segment assumed to be C unless otherwise indicated;  
   
                                    
if you can count to 4, you can figure the # of H’s on each C];  
   
                          other elements or functional groups [N, O, S, CO2H, Cl, etc.] 
   
                             indicated with  symbol and line representing bond to appropriate
   
                              carbon atom.  

 Once you get used to them, these are often the most convenient way to quickly draw
   
                                 
complex structures; we’ll be using them extensively.  

 The different ways of depicting organic structures are discussed by Bill Robinson of Purdue University at 
http://chemed.chem.purdue.edu/organic/topicreview/structures/index.html 

IV.  Alkanes: the simplest hydrocarbons, & the foundation for everything else that follows!

Click here to see a table of alkanes

           A.   Methane  CH4 :   structure,  bonding,  and geometry  
           B.
   Higher “straight-chain” alkanes  [S&S table 1.4, p.16] : conformation = shape
 

Chime illustrations of alkanes by Jason Camara at Cabrillo College
http://c4.cabrillo.edu/chem30b/comp_resources/Reference1.html#straight


           C
.   Structural  Isomers: the possibilities increase due to branching   

To see a large number of alkane Chime structures, go to Dave Woodcock's site
at OUC [
Okanagan University College]:
Use Netscape 4.7x with Chime installed for these!! 
 http://www.molecularmodels.ca/molecule/Alkanes.htm

and particularly relevant to this section is his "Molecular Fragments: Alkane Isomers" page at  
http://www.molecularmodels.ca/molecule/molfrag/mf009.htm

D.   Alkane  nomenclature: now and forever!  

You will find a trip to Dave Woodcock's nomenclature site at  OUC very worthwhile -- 
http://www.molecularmodels.ca/nomenclature/index-2.htm
Use Netscape 4.7x with Chime installed for these!! 

            E.   Cycloalkanes: structure, nomenclature, geometric isomers

Click here to see a table of cycloalkanes

 To see Dave Woodcock's Chime structures of cycloalkanes and related compounds, go to
http://www.molecularmodels.ca/molecule/Cyclic_(non-aromatic).htm
Use Netscape 4.7x with Chime installed for these!! 

Chime material on cycloalkanes by Jason Camara at Cabrillo College
http://c4.cabrillo.edu/chem30b/comp_resources/Reference2.html#cycloalk

            F.   Physical properties of alkanes   

                    For many physical properties, the determining factor is the strength of the
                                 intermolecular attractive forces.

             G.  Chemical properties [reactions] of alkanes 
                       
1.  Combustion
                                    an extreme form of oxidation of paramount economic and ecological significance.  

Dr. Ron's magic formula for balancing combustion equations for any HYDROCARBON

since C + O2 à CO2  and  2H2 + O2 à  2H2O,  it can readily be shown that

CxHy + (x + ¼·y)O2  à  xCO2 + ½yH2O
 

Combustion from the Virtual Textbook of Organic Chemistry by William Reusch at Michigan State U
http://www.cem.msu.edu/~reusch/VirtualText/funcrx1.htm#combust


   
                     2.     
Halogenation:  where does that Freon come from, anyway?  

V.   Beyond hydrocarbons:  FUNCTIONAL GROUPS:  
                           
[DCT Table 11.2; S&S table 1.2, p.8]     

                                just look for now and worry about them later!    

Functional groups by Mark Bishop at MPC
http://www.mpcfaculty.net/mark_bishop/Chemistry_10.htm > Chapter 17
Functional groups from Purdue University
http://chemed.chem.purdue.edu/organic/topicreview/functiongrps/fungroupframe.html
A really nice Chime-based table of functional groups by Jason Camara at Cabrillo College
http://c4.cabrillo.edu/chem30b/comp_resources/functional_table.html

            

CLASS

CHARACTERISTIC GROUP

TYPICAL GROUP STRUCTURE

Alkyl Halides or haloalkanes

RX, where X = F, Cl, Br, I


   

Alkenes

C=C


  

Alkynes

CC

 
 

Aromatic

C6H5


Alcohols

ROH

 

   

Ethers

ROR’


Thiols  
or mercaptans

RSH


Aldehydes

RCHO or RC(=O)H


   

Ketones

RCOR’ or RC(=O)R’


Amines

RNH2, R2NH, R3N

 
 

Carboxylic Acids

RCO2H


Esters

RCO2R’

 

Amides

RCONHR’

 
 

Heterocyclics

take a look à


  

   these functional groups and other such goodies increase the number of possible organic structures horrendously. Don’t fret about them right now; each gets its very own chapter later on!  

Suggested homework problems for Chapter 11
1-14 [mixed in with text]
15, 16, 17ac, 18b, 19bd, 20, 29ace, 30dfh, 31beg, 32bd, 33, 35, 36a, 39bg, 40ac, 47b, 55ab, CTP1

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© Ronald W. Rinehart, 2002-2007