Summary from Organic Chemistry Packet: Introduction to organic chemistry.
Science Bowl Organic Chemistry Notes
Transcript of Science Bowl Organic Chemistry Notes
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Aliphatic Functional Groups to Know and Love
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Common Aromatic Compound Names
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Nomenclature Roots
Meth- (Me)/Form- : -CH3
Eth- (Et)/Acet- : -CH2 CH3
Prop- (Pr) : -CH2 CH2 CH3
But- (Bu) : -CH2 CH2 CH2 CH3
Pent- : -CH2 CH2 CH2 CH2 CH3
Hex- : -CH2 CH2 CH2 CH2 CH2 CH3
Hep- : -CH2 CH2 CH2 CH2 CH2 CH2 CH3
Oct- : -CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3
Non- : -CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3
Dec- : -CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3
Undec- : -CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3
Dodec- : -CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3
Tridec- : -C13H27
Tetradec- : -C14H29
Pentadec- : -C15H31
Hexadec- : -C16H33
Heptadec- : -C17H35
Octadec- : -C18H37
Nonadec- : -C19H39
Eicos- : -C20H41
Triacont- : -C30H61
Tetracont- : -C40H81
Pentacont- : -C50H101
Decacont- : -C100H201
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Structural Formulas
Molecular FormulaA count of each atom type. Molecular formulas can represent
multiple compounds. Ex: C2H4O
Kekule StructuresStructures that show the position of every atom and bond.
Condensed StructuresStructures that group functional groups together.
Alternatively:
What about larger compounds?
Line structuresStructures where carbons are represented by ends and corners
unless otherwise indicated. Hydrogens bonded to carbons are implied. All otheratoms are shown.
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Alkanes (C-C)
Saturated hydrocarbonsEach carbon has the maximum number of hydrogens
present. Formula:
Unsaturated hydrocarbon: At least one carbon has fewer than the maximumnumber of hydrogens allowed.
Properties of Alkanes
Intermolecular Forces:
Polarity:
Boiling Point:
Solubility:
Acidity/Basicity:
Hybridization and VSEPR Geometry:
Valence Bonds:
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IsomersDifferent molecules with the same molecular formula.
Constitutional IsomersIsomers that differ in connectivity.
C4H10:
C5H12:
Degree of Branching
Primary carbons (1o) will have ____ bonds to a carbon.
Secondary carbons (2o) will have ____ bonds to carbons.
Tertiary carbons (3o) will have ____ bonds to carbons.
Quaternary carbons (4o) will have ____ bonds to carbons. These are rarely reactive.
In the case of double and triple bonds, each pi bond counts as one bond.
Functional groups will adopt the degree of branching of the carbon they are bondedto.
In the molecule below, circle the 2o carbon(s). Box the 3o carbon(s). Draw anarrow to the 4ocarbon(s). Dont disturb the 1o carbon(s).
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Alkane Nomenclature
1. Identify the largest continuous chain of carbons. This is called the parentchain.
2. If there are two series of carbon of the same length, rings take priority overchains.
3. Identify the substituents and number the carbons on the parent chain so thatthe substituents have the lowest possible numbering.
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If the substituent is a carbon chain, name it as a parent chain and replace
ane withyl.
4. List substituents alphabetically. Ignore prefixes.
5.
Replicated substituents are grouped together using di-, tri-, tetra-, penta-,hexa-, hepta-, etc. The prefix is not used to alphabetize substituents.
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6. Common substituents:OH = hydroxyl NH2 = amino CN = cyano
Cl, Br, F = chloro, bromo, fluoro NO2 = nitro
Name the following compound:
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Cycloalkanes
Cycloalkanes have the same properties as alkanes. The formula of a basic
cycloalkane is:
Angle strainThe energetic resistance of bond angles to deviate from theirVSEPR angles
Cyclopropane and Cyclobutane:
High angle strain = unstable
sp3-hybridized carbons prefer _______ bond angles
Planar or puckered (cyclobutane only) conformations (3-D geometries)
Cyclohexane:
The angles of a regular hexagon are _______; therefore, cyclohexane will prefer to
adopt a 3-D shape to minimize angle strain.
________ conformations are the _______ stable conformations of cyclohexane.Cyclohexane can have ___ two possible conformers of this type that can
interconvert between each other.
Axial sites - __________ to the cyclic plane, alternate up and down. Substituents inthe axial position make the cyclohexane ______ stable.
Equatorial sites - __________ to the cyclic plane, alternate up and down.Substituents in the equatorial position make the cyclohexane ______ stable.
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Label the sites below as axial or equatorial.
Why are conformers with substituents in the equatorial position more stable?
Steric hindranceWhen the size of a large substituent competes for space with an
adjacent group. This can lead to limited chemical reactivity and instability
t-butylcyclohexane
Substituent in axial position Substituent in equatorial position
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Dash ( )indicates atoms going ________ or ________ the plane of paper
Wedge ( )indicates atoms going ________ or ____________ the plane of
paper
Two substituents are ______ to each other when they are going in the same
directions. They are ______ to each other when they are going in differentdirections.
Draw planar representations of the two molecules above.
Out of all cycloalkanes, cyclohexane will experience the least strain in its bonds;smaller cycloalkanes will suffer from angle strain, and larger cycloalkanes will
experience strain from steric hindrance of its substituents.
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Bicyclic moleculesMolecules with two rings that share a side
Spiro moleculesMolecules with two rings that share an atom
Bridged moleculesMolecules with three rings that share two atoms with each
other
Heterocyclic moleculesMolecules with a ring in which a carbon has been
replaced with any non-carbon atom.
Classify the following molecules:
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Alcohols and Alkyl Halides (R-CH2-OH)/(R-X)
Properties of alcohols/alkyl halides:
Intermolecular Forces
Polarity
Boiling Point
Solubility
Acidity/Basicity
Hybridization
Nomenclature
For alcohols, list the group as a substituent or use the alcohol as part of the parent
name by replacing the laste withol.
For alkyl halides without hydroxyl groups, list the group as a substituent or replace
theane of the parent chain withyl, then replace theine of the halogen with
ide.
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A special note on alcohols: _____ alcohols can oxidize to aldehydes, while _____
alcohols can oxidize to ketones.
Random fact: heating an alcohol in the presence of a strong acid will produce analkene. Such types of reactions where alkenes are formed from taking out two
substituents on adjacent carbons are termed ________________ reactions. For
example:
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Stereochemistry
StereoisomersCompounds with the same formula, constitution, and functional
groups in the same place but have a different orientation in space
A molecule is termed __________when it isnt superimposable on its mirror
image. The center of stereochemistry is typically ______ -hybridized. Typically,
but not always, a molecule will be chiral if a carbon has _____ different
substituents bonded to it
EnantiomersTwo molecules that are mirror images of each other but are not
super-imposable
In an achiral environment, enantiomers will behave identically and have the same
physical properties except for their rotation of ____________________________.
Racemic mixture: a ________ mixture of two enantiomers. These will not rotate
light.
Molecules that rotate light clockwise are termed dextrorotatory and are indicated
by a (+) in front of their name.
Molecules that rotate it counterclockwise are termed levorotatory and are indicated
by a (-) in front of their name.
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Enantiomers can also be named with the R/S or E/Z systems. Names are
determined based on the molecular masses of substituents and their spatial
arrangement relative to each other.
Finally, they can be named with the L/D system, where the name of the compound
is determined based on whether the compound forms from the L or D enantiomer
of glyceraldehyde.
Diastereomerstwo stereoisomers that are not mirror images to each other. These
have at least ____ chiral centers
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Alkenes (C=C)
Formula:
Properties
Hybridization:
Valence Bonds:
All other properties are similar to those of ________________.
Nomenclature
Name the alkene like you would an alkyl chain, but drop theane and addene.
The parent chain must contain the double bond. Be sure to indicate which number
carbon starts the double bond.
Vinyl alkenes, or terminal alkenes, have a double bound at the end of a chain. Allyl
alkenes have a double bond at a 2-carbon. Note: alkenes dont necessarily have to
be either vinyl or allyl.
Indicate which of the above alkenes are vinyl or allyl.
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In alkanes, carbon-carbon sigma bonds can rotate freely. However, alkenes cant
rotate due to the necessity of massive energy to break pi bonds. This introduces the
possibility of ________________ isomers.
When the two heaviest substituents on opposite carbons in a double bond are on
the same side of the double bond, _________ or ______ is written before their
names. If they are on opposite sides and are diagonal to each other, _________ or
______ is written before their names. In general, the _______ isomer of an alkene
will be more stable than the _______ isomer.
Fun fact: alkenes are popular compounds for undergoing ____________________
reactions, where the double bond is broken by adding a substituent to each sp2-
hybridized carbon of the said pi bond. Three of many types of these reactions are
given below:
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Formula-
Properties
Acidity/Basicity
Hybridization
Valence Bonds
All other properties are similar to those of _______________________________.
Nomenclature
Name the alkyne like you would an alkene, except replaceene withyne.
An alkyne that has the formula RC2H is classified as _______________ alkynes.All others are _________________ alkynes.
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Acidity of terminal alkynes
Protons on terminal alkynes are more easily extracted than those on alkenes and
alkanes because the triple bond has _______________ character.
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Dienes
A diene is an alkene with ______ carbon-carbon double bonds.
____________ dienea diene with double bonds that act independently of each
other. The double bonds are always at least ______ carbons away from each other.
____________ dienea diene with double bonds _______ carbon away from eachother. The pi electrons delocalize*, making the diene very _____________.
____________ dienea diene where a carbon atom has _____ double bonds. The
pi bonds are perpendicular to each other and require a lot of energy, making the
diene very _____________.
*In organic chemistry, electron delocalization will always lead to compound and
ion stability. These electron delocalizations always occur within the pi orbitals and
can occur in compounds with adjacent double bonds or with a series of adjacent pi
bonds and electric charge, radical electrons, or lone pairs. These structures will
always have multiple resonance structures. In other words, compounds that show
resonance have electron delocalization, which stabilizes them.
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Diels-Alder Reaction
A ______________ diene will react with an______________, in this case termed a
______________, to form a ___________________.
Cycloalkenes
Cycloalkenes are carbon rings that include one double bond between two carbons
in the ring. Their general formula is _____________________. These cycloalkenes
dont undergo conjugative delocalization of pi electrons and thus dont exhibit
resonance (such structures are discussed in the next section.
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Aromaticity
Compounds are said to be _______________ when it contains a conjugated ring of
delocalized pi electrons that increase the stability of the compound. (It will thus
show resonance)
A special note on benzene
After experimentation, August Kekule determined the following in relation to
benzene:
1. Benzenes molecular formula is C6H62. All the hydrogens on benzene are equivalent3. The octet rule requires that there be four bonds to each carbon
Kekule then hypothesized the following structures for benzene:
However, a flaw was soon discovered in the structure. Kekules structure suggests
that the following compounds would have different properties:
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The structure implies that a single bond connects the carbons of two substituents in
one isomer and a double bond connects the carbons in the second.
However, no such cases of isomerism were known, and none could be found.
Kekule therefore proposed that two isomers could exist but interconverted too
rapidly to be noticed:
We know that this isnt the case. Experiments show that all of the carbon-carbon
bonds in the ring are energetically equivalent and have a bond length of 140 pm,
exactly halfway between the sp2-sp2 double bond length of 134 pm and the sp2-sp2
single bond length of 146 pm.
The two structures correctly show the arrangement of atoms, but they differ in the
placement of electrons. Thus, they are resonance structures, and neither shows the
correct bonding of benzene by itself. We therefore know that the hybrid structure
of benzene has the following appearance:
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The bond angles in benzene are _________, the angles of a regular hexagon. Since
________-hybridized atoms prefer these angles, benzene will remain planar
instead of twisting into a 3-D shape like cyclohexane. Furthermore, the conjugative
delocalization of pi electrons enhances benzenes stability to such a degree that the
bonds within the ring all act together as one functional group instead of six
separate bonds.
A Demonstration of Aromatic Stability
Cyclohexanol Deprotonation -
Phenol Deprotonation -
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Nomenclature
In monosubstituted benzene derivatives, if using benzene for the parent chain, treat
substituents like you would with an alkane.
If using benzene as a substituent, name it a phenyl (Ph) group.
If using benzene attached to one carbon, name it a benzyl (Bz) group.
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For disubstituted benzene derivatives, use ortho- or o- if the substituents are
next to each other, meta- or m- if the substituents are separated by a hydrogen,
and para or p- if the substituents are on opposite ends of the ring.
For trisubstituted derivatives and above, use the numbering system.
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Refer to the table of benzene derivatives at the beginning of this packet for more
common benzene derivatives.
Friedel-Crafts Alkylation/AcylationAlkylation:
Acylation:
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Ethers (R-O-R)
Properties of Ethers
Intermolecular Forces:
Polarity:
Boiling Point:
Solubility:
Acidity/Basicity:
Hybridization and VSEPR Geometry:
Valence Bonds:
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Compound Structural
Formula
Dipole
Moment (D)
Boiling Point
(oC)
Solubility in
H2O(g/100 mL)
Dimethyl ether CH3OCH3 1.3 -24 0.071
Propane CH3CH2CH3 0 -42 0.004
Ethanol CH3CH2OH 1.69 78 Miscible
Nomenclature
If naming the ether as a substituent, take the smaller chain attached to the oxygen,
replaceane withoxy, and add the name of the parent chain after it.
If naming the ether as a functional group, replace theane of the side chains with
yl, write them alphabetically, and add ether. If both side chains are the same,
write di and then the side chain once before writing ether.
Cyclic Ethers and Epoxides
The carbons attached to the ether oxygen can be bonded to other chains that form a
ring. These ethers are called cyclic ethers. Example: Tetrahydrofuran (THF)
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Epoxides are a special type of cyclic ethers where the carbons bonded to the ether
oxygen are also bonded to each other. Epoxides tend to be ____________ because
of ____________________. Example: oxirane, 1,2-epoxycyclohexane
Aldehydes and Ketones (RH=O)/(RR=O)
Properties of Aldehydes and Ketones
Intermolecular Forces:
Polarity:
Boiling Point:
Solubility:
Acidity/Basicity:
Hybridization and VSEPR Geometry:
Valence Bonds:
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Nomenclature
For aldehydes, name the compound like you would an alkyl chain and replace the
ane withal.
For ketones, name the compound like you would an alkyl chain and replace the
ane withone.
If a compound contains both an aldehyde group and a ketone group, the aldehyde
takes priority. Use oxo- to name the ketone group substituent.* Be sure to mark
the # carbon the ketone is on.
*Something useful to know: any C=O group is called a ________________ group.
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Aldehydes and ketones will oxidize to ____________________ and ___________
respectively. They will reduce to _________________________ and
________________________ respectively.
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Carboxylic Acids and Esters (RCOOH)/(RCOOR)
Properties of Acids and Esters
Intermolecular Forces:
Polarity:
Boiling Point:
Solubility:
Acidity/Basicity:
Nomenclature
For carboxylic acids, name the acid like you would an alkyl chain, then drop the
ane and add -oic acid.
For esters, list the chain bonded to the oxygen as a substituent, then name the
parent like you would an alkyl chain. Replace thee on the end of the parent chain
withoate.
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Carboxylic acids and esters will reduce to ______________ and _______________
respectively.
Fischer Esterification
Perhaps the most common way to prepare esters is through the Fisher
Esterification, which involves an equilibrium reaction between a carboxylic acid
and an alcohol. Note: the acid will retain both of its oxygens and lose only the
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proton bonded to the second oxygen, while the alcohol will lose its hydroxyl
group.
Saponification- KNOW THIS
Although soap has many ingredients that contribute to its properties, the main
active molecule involves an anion with a polar carboxylate head and a nonpolarfatty acid tail bonded to a sodium or potassium cation. The structure of the sodium
salt is displayed below:
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Common carboxylate salts:
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When in water, these sodium/potassium salts dissociate. The nonpolar fatty acid
tails of the carboxylates are hydrophobic and thus prefer to bond intermolecularly
with other fatty acids, forming a sphere coated with polar heads and filled with
fatty acid tails. These spheres are termed micelles.
We use soap to wash our skin because nonpolar compounds on our skin wontbond to the water and fall off due to strong intermolecular forces. When we scrub
soap on our skin, the micelles break, and the fatty acid tails bond to the nonpolar
substances. The micelles re-form with the unwanted residue trapped inside, and the
polar heads hydrogen-bond with water to carry the substances away.
Whether sodium or potassium is used to make the soap does have an effect on the
product. In general, a sodium salt will produce solid soap, which will be treatedwith further chemicals to form a bar. A potassium soap will typically be liquid,
which will be treated to form a soap gel.
Fatty acids are normally found in the form of triglycerides instead of monomers. In
the laboratory, saponification typically occurs by reacting a vegetable oil, a reliable
source of triglycerides, with sodium hydroxide in the presence of water, ethanol,
and heat. Sodium hydroxide by itself is a caustic solid and must be dissolved with
water to react. In addition, triglycerides do not dissolve in water, limiting the
saponification reaction to the surface, so ethanol is added to dissolve the
triglyceride into the aqueous solution. Finally, saponification is an endothermic
reaction and requires an external source of heat for the reaction to occur.
The basic chemical reaction for in-lab sodium saponification is displayed below:
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Amines
Properties of Amines
Intermolecular Forces:
Polarity:
Boiling Point:
Solubility:
Acidity/Basicity:
Hybridization and VSEPR Geometry:
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Nomenclature
There are two ways to name amines where the nitrogen is bonded to only one
carbon (primary amines): in the alkanamine system, take the parent chain, drop the
laste, and addamine. In the alkylamine system, replace theane of the parentchain withyl and add amine to the end. Remember to denote the location of the
amine with numbering in both cases.
Note: amines bonded to phenyl rings are called anilines.
Other amines are named as N-substituted derivatives of primary amines. Theparent chain is taken to be the one with the longest carbon chain. Rings, however,
take precedence over chains.