[covers all classes of compounds from Chapter 11 through 16]:
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
the –oic 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.
© Ronald W. Rinehart,
2002 Structures drawn with MDL IsisDraw