CHEM 30B  Dr. R. Rinehart    EXAM 2 Study Guide   3/20/02 

READ THIS GENERAL STATEMENT CAREFULLY:

            Your mission in this course is to obtain for yourself a useful working knowledge and understanding, at an appropriate level, of some basic organic chemistry and biochemistry, as outlined in the syllabus and subsequently elaborated in class. The resources available to you include the text, lectures and class handouts, laboratory exercises, references in print and on the internet, consultation with the instructor outside of class, tutors on duty in PS-205, or by arrangement, and whatever other legitimate means are necessary. There is no easy path to success. Put the work in. It is particularly important to pay attention to the following sections at the end of each chapter: Summary, Key Terms, and Reactions. In particular, the learning objectives tell you what types of knowledge you will be expected to demonstrate.  You will not be able to demonstrate them unless you understand the principles involved! Similarly, you will find it pointless to memorize key terms without knowing what they “Right, sure, yeah, yeah, yeah – just tell us what’s going to be on the test, doc.”
What
?  Questions designed to show if you have learned to use these principles and their associated language.
How
? Generally by means of objective questions in a variety of formats: fill-ins, short answers, matching, multiple choice, true-false, listing, categorizing, prioritizing, and problem-solving are all possibilities. Naming compounds, drawing structures and/or diagrams, writing (and sometimes balancing) equations, and making rational deductions  are all possibilities. 

Chapter 14: Aldehydes and Ketones [also Aldehyde/Ketone Lab] 

            both contain the carbonyl (C=O) group ; aldehydes have H attached to C=O,
                    ketones have C’s on both sides of C=O 

            Nx:  aldehydes: the HCO group’s C is position #1 of the longest chain containing it;  drop –e
   
                 from alkane stem name and add –al. locate and number other substituents.
                    Aromatic aldehydes: based on benzaldehyde 

                    ketones:  find longest chain containing the C=O, give it the lowest possible number, then
   
                      locate and number other substituents. Drop –e from alkane stem name and add –one.
                            common system: name the two groups on either side of the C=O, followed by “ketone”. 

important examples and their uses: methanal [formaldehyde] embalming, making plastics;
                       
ethanal [acetaldehyde] hangovers and cell damage from ethanol consumption;
                       
2-propanone [acetone] and 2-butanone [methyl ethyl ketone] important industrial solvents;
                       
retinal [vitamin A] critical for vision and other life processes;
                       
fragrant compounds on pp. 123-124. 

            physical properties: C=O is polar, but cannot H-bond with itself, 
                    ∴
m.p., b.p. higher than hydrocarbons but lower than alcohols.
                        CAN H-bond with water, so RCHO and RCOR’with < C4 are soluble in water.
                        Wide variety of odors: ketones usually pleasant.                
   
         chemical properties:  See Key Reactions, pp 126-127.
   
                     •  formation: aldehydes by oxidizing 1o ROH, ketones by oxidizing 2o ROH
   
                     aldehydes can be further oxidized to carboxylic acids, ketones can’t.
                        • Basis of Tollens’ [Ag+ à Ag0] and Benedict’s [Cu2+ à Cu+] tests [see lab sheets]
                        • C=O can add ROH to double bond to give hemiacetals or hemiketals [reversible rxn];
   
                             dehydration of these with second molecule of alcohol yields acetals or ketals,
                                which can be hydrolyzed to give back starting compounds.
                        • These rxns are important in carbohydrate [polyhydroxy aldehydes/ketones] chemistry;
                                most simple sugars [monosaccharides] exist as intramolecular [and therefore cyclic]
                                hemiacetals or hemiketals.
                                   
more complex sugars [disaccharides and polysaccharides] can be made by reacting
                                               
the hemiacetal/hemiketal group of one monosaccharide unit with one of the
                                               
-OH groups on a second monosaccharide unit, forming an acetal or ketal.
                       
Reaction with –NH2 groups: lose H2O and form C=N linkage [see lab sheets] 
                                attachment of retinal to opsin to form rhodopsin occurs like this.           
       

Chapter 15: Carboxylic Acids and Esters 
[also Ester Lab and Acid/Ester Workshop]

The carboxyl group –CO2H is the highest priority group; its various derivatives [anhydride,
                 
acyl chloride, ester, amide, etc.] have next highest priority. 

Group priorities for nomenclature/numbering 
[covers all classes of compounds from Chapter 11 through 16]
:

                        Y = OR’, Cl, Br, S                                                                                    
                        
  OCOR’, …..
 

Nx: monocarboxylic acids: -CO2H group’s C is position #1 of the longest chain containing it; 
   
                 drop –e from alkane stem name [which you should know for C1 to C22!] and add –oic acid.
   
                  locate and number other substituents. Know common names for C1 to C4. Long-chain [> C12]
                     are called “fatty” acids; those with several C=C (18:2, 18:3, 20:4, 20:5, 22:6) can be diet-
                     essential;
know them!

            
       dicarboxylic acids: the two –CO2H define the “longest” chain; drop –e from alkane stem name
   
                      [which you should know for C1 to C22!] and add –dioic acid. locate and number other
   
                      substituents. Know common names for C1 to C6.
            
       anhydrides: use common or IUPAC name of acid and add anhydride.
            
       acyl chlorides: modify name of corresponding acid: drop –e from alkane stem name and add
   
                          –oyl chloride.
   
                esters:  Identify the “alcohol” and “acid” parts of the molecule and name in that order; the
   
                         alcohol name ends in –yl and the acid name ends in –ate.  [e.g. 2-butyl pentanoate] 

physical properties:  

        RCO2H:  H-bonding causes dimer formation, very high m.p., b.p. relative to
   
                          RH. <C10 liquids, larger solids UNLESS cis-C=C in chain.  Odors usually sharp, unpleasant.
                    Esters:  usually liquids, generally pleasant odors. moderately polar, make good solvents.
                            Esters of glycerol and fatty acids are called (tri)glycerides: animal/vegetable fats & oils 

            chemical properties:  RCO2H:  characteristic reactions: 
   
                     • dissociation [ionization] in water to give H3O+  [know acid-base definitions!!!!] 
                        • neutralization by bases to give carboxylate salts & H2O.  
   
                     • Intermolecular dehydration with R’OH to give esters [also formed from R’OH using
   
                             anhydrides or acyl chlorides]. Dicarboxylic acid + diol
à polyesters
                            Esters can be hydrolyzed using acid catalyst [products: RCO2H + R’OH] 
                                or with base [saponification = “soap-making”]  product RCO2-M+ .
                       
Salts of fatty acids are soaps: understand how they work.
           

Chapter 16: Amines and Amides [also Amine/Amide Workshop] 

 Amines: contain nitrogen group attached to C in an alkyl group

            Classes: 1o, 2o, 3o  based on # of C’s directly attached to N. 
   
                         4o ammonium compounds R4N+  have “permanent” + charge on N
                    “alkaloids” are nitrogenous bases of plant [occasionally animal] origin with profound
   
                             physiological effects.

            Nx:  several methods
                        1)
attach suffix –amine to stem name of longest chain containing the –NH2, which gets
                                lowest number available.  e.g. CH3CH2CH2CH2NH2 is butanamine.
            
            2) use prefix amino-  with lowest number locant and hydrocarbon name [1-aminobutane]
                       
3)  use common names of alkyl groups with the ending amine  [n-butylamine]
                       
4) for 2o and 3o amines, whether using system 1 or 2, the prefix N- is used to emphasize
                                   
attachment of a group to the nitrogen. CH3CH2CH2CH2NHCH2CH3 is
                                   
N-ethyl butanamine or 1-(N-ethylamino)butane.
   
                                 Common name n-butyl ethyl amine
                       
5) Aromatic amines: Usually named as derivatives of aniline C6H5NH2
                               
6)  Heterocyclics: you should be familiar with the following: pyrrole, pyrrolidine, pyridine,
                                    piperidine, pyrimidine, purine, indole, imidazole.
We'll be seeing them again!

            physical properties:  can H-bond to themselves and to water, so m.p., b.p. > for RH, but < for ROH.
                       
Those with < C4 water-soluble. Almost all simple amines have terrible, fishy odors.
           
chemical properties:  amines are weak bases; form ammonium salts with acids. 
                       
Intermolecular dehydration of  NH3 or 1o or 2o amine with carboxylic acid yields amides,
                                   
[which can also be formed from anhydrides or acyl chlorides]. 
                        Reaction of  dicarboxylic acids with diamines yields polyamides [nylon, Kevlar, etc.]
   
                                 Polyamides can also be formed using bifunctional momomers [containing both
                                    carboxyl and amino groups
           
biological properties:  many amines or ammonium compounds act as neurotransmitters (pp.174-178)                         specific alkaloids can mimic or antagonize these actions, thus can be useful medicines or
                       
drugs of abuse or deadly poisons. 

Amides:  Nx: change theoic or –ic ending of corresponding acid to –(o)amide; if N has additional groups,
                       
place names of groups prefixed by N-  at front of name. 
                        E.g., CH3CON(CH3)2 is N,N-dimethylacetamide or N,N-diethylethanoamide

           
physical properties:  can H-bond, so usually unsubstituted amides are solids; very low-m.w. are
   
                      water-soluble.
           
chemical properties:  can be hydrolyzed using either acidic or basic conditions; more stable to
                       
hydrolysis than esters.

           
biological properties:  the amide bond is what joins amino acids together to form proteins.

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© Ronald W. Rinehart, 2002 Structures drawn with MDL IsisDraw