CHEM 30B  Dr. R. Rinehart

Chapter 3  ROH, ArOH, ROR’ , RSH

ALCOHOLS, PHENOLS, ETHERS, THIOLS, …

 

Some Compounds with Oxygen, Sulfur, or a Halogen
-- Slides by Warren Gallagher at the University of Wisconsin, Eau Claire
http://www.chem.uwec.edu/Chem150_S06/Pages/lecture-materials.html > Lecture 3
Alcohols, ethers, and thiols by Gary Trammell and Srinivas Vuppuluri
at the University of Illinois at Springfield
http://people.uis.edu/gtram1/organic/alcoholsmenu.htm 
 
 

            This chapter is our first real exposure to non-hydrocarbon organic compounds, other than haloalkanes, and centers on compounds containing oxygen singly bonded to carbon; the three classes of compounds can be viewed as organic derivatives of water  in  which  one  (alcohols, ROH  and phenols, ArOH)  or  both  (ethers, R-O-R’) hydrogens have been replaced by alkyl or aryl groups. These compounds are of great industrial, economic, and biological importance. Since sulfur is directly below oxygen in the periodic table, we will also look at thiols (RSH) and disulfides (RS-SR’), compounds of extreme biological significance. Finally, we will begin to examine multifunctional compounds, those which simultaneously belong to more than one class.

  See the learning objectives 

I. ALCOHOLS (Sect 3.1 to 3.5)

            A. Structure: contain a hydroxyl group attached to carbon

            B. Nomenclature: replace the -e in the stem name with -ol; CH3OH is methanol;

                        Number the longest chain containing the -OH group in such a way that the hydroxyl
                       
group gets the lowest number.  e.g., (CH3)2CHCH2CH2CHOHCH2CH3 is
                       
6-methyl-3-heptanol, not 2-methyl-5-heptanol.  

(See table of alcohols for examples)

See Dave Woodcock’s Chime structures of alcohols at OUC at http://www.molecularmodels.ca/molecule/Alcohols.htm 

              C. Classification of alcohols: important, because they don’t react the same way

                        1. Primary: the OH-bearing C is directly connected to only one other C (e.g., 1-pentanol)
                                   
methanol
is considered to be a “special case”

                        2. Secondary: the OH-bearing C is directly attached to two other carbons (e.g., isopropanol)

                        3. Tertiary: the OH-bearing C carries three other carbons (e.g., 2-methyl-2-butanol)

 

           

D. Physical properties [see Fig. 3.2, 3.6, and 3.3, 3.4, and 3.5]

                        1. Solubility in H2O: C1 toC3: miscible; C4 to C6: soluble; >C6; insoluble

                        2. Melting and boiling points much higher than corresponding alkanes (H-bonding)

                        3. Soluble in other alcohols, ether, acetone, etc.

            E. Reactions [see “Study Skills 3.1”, p. 85]

                        1. Dehydration (with sulfuric acid)

                                    a. Intramolecular: yields alkenes  3o > 2o > 1o

                                    b. Intermolecular: yields ethers

                                    c. Biological examples

                        2. Oxidation [review the three definitions]

                                    a. Complete = combustion; low-m.w. burn with blue (clean) flame;.gasohol

                                    b. Partial: with oxidizing agents like CrVI, ( or NAD+ in biological systems)

                                                1o  (RCH2OH)----à   aldehydes (RCHO)---à carboxylic acids(RCO2H)
           
`                                  
2o  (R2CHOH) ---------à   ketones  (R2C=O)
                                               
3o  (R3COH)             no reaction

            F. Uses: solvents, starting materials, cosmetics, antifreeze see table 3.2, p 88

II. PHENOLS (Sect 3.6) have the –OH group directly attached to an aromatic ring

            A. Examples and nomenclature

            B. Properties/ uses: disinfectants and antioxidants

See table for examples

See Dave Woodcock’s Chime structures of phenols at OUC at  http://www.molecularmodels.ca/molecule/Phenols.htm  

III. ETHERS  (sect 3.7, 3.8)

            A. Structure and nomenclature: identify and name the groups flanking the Oxygen

            B. Properties and uses
                       
less polar than alcohols, more polar than hydrocarbons : make
good solvents
                       
highly flammable; otherwise, not too reactive:    make good solvents  
                       
diethyl ether: the original general anesthetic

See table for examples

See Dave Woodcock’s Chime structures of ethers at OUC at http://www.molecularmodels.ca/molecule/Ethers.htm 

  IV. THIOLS (RSH) and DISULFIDES (RS-SR’)   See Sect 3.9

            A. Nomenclature:  3-methyl-1-butanethiol  (CH3)2CHCH2CH2SH  is  “essence of skunk”

            B. Interconversion by redox:  2RSH + [O] à RS-SR;  RS-SR + [H] à  2 RSH

            C. Biological significance: protein structure & enzyme action; affinity for heavy metals

See table of thiols

To learn more about the chemistry of skunk spray, see William F. Wood’s site at Humboldt State University   http://www.humboldt.edu/~wfw2/chemofskunkspray.html

  V. POLYFUNCTIONAL COMPOUNDS: they are the rule in biological systems

            A very few examples that we have seen:

cholesterol [polycyclic, alkene, alcohol]
           
glucose [aldehyde, polyol]
           
tyrosine [phenol, amine, carboxylic acid]
            cysteine [thiol, amine, carboxylic acid]
            THC [phenol, polycyclic, ether]
           
vitamin E [phenol, polycyclic, ether]  

See the learning objectives

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  © Ronald W. Rinehart, 2002, 2006