Organic Chem Ch 3 and 5

acyclic
noncyclic
alkane
A saturated hydrocarbon; a hydrocarbon that has no carbon – carbon multiple bonds; has only carbon-carbon single bonds; formerly called the paraffin series.
alkyl group
the group of atoms remaining after a hydrogen atom is removed from an alkane: an alkane-like substituent . symbolized by R
amyl
an older common name for pentyl
angle strain or baeyar strain
the strain associated with distorting bond angles to smaller or larger angles
anti conformation
the geometric arrangement around a carbon-caron single bond in which the two largest substituents are 180 degrees apart as viewed in a Newman projection
aromatic hydrocarbon
a hydrocarbon having a benzene-like aromatic ring
axial bond
one of the six bonds (three up and three down) on the chair conformation of the cyclohexane ring that are parallel to the “axis” of the ring
The axil bonds are shown in red, and the equatorial bond is green
bridged bicyclic compound
a compound containing two rings joined at nonadjacent carbon atoms
bridgehead carbons
the carbon atoms shared by two or more rings. Three chains of carbon atoms (bridges) connect the bridgeheads
chair-chair interconversion
(ring-flip) the process of one chair conformation of a cyclohexane flipping into one another , with all the axial and equatorial position reversed . the boat (or twist boat) conformation in an intermediate for the chair -chair interconversion
cis-trans isomers
(geometric isomers) stereoisomers that differ only with respect to their cis or trans arrangement on a ring or double bond
cis:
having two similar groups directed toward the same face of a ring or double bond
trans:
having two similar groups directed towards opposite faces of a ring or double bond
combustion
a rapid oxidation at high temperatures in the presence of air or oxygen
common names
the names that have developed historically, generally with a specific name for each com compound: also called trivial names
conformational analysis
the study of the energetics of different conformations
conformations and conformers
structures that are related by rotations about a single bond. Strictly speaking, a conformer is a conformation that corresponds to a relative minimum energy usually a staggered conformation. In most cases , conformations and conformers interconvert at room temperature, and they are not true isomers
Know the conformations of cyclohexanes
chair
half chair
boat
twist boat
chair conformation
conformation of cyclohexane with almost no angle strain resembles a chair, all neighboring C-H bonds are staggered – most stable
boat conformation
the less stable puckered conformation of cyclohexane, with both parts puckered upward. The most stable boat is actually the twist boat ( or simple twist) conformation. Twisting minimizes torsional strain and steric strain
flag pole hydrogens
two hydrogens (blue) in the boat conformation point upwards like flagpoles. the twist boat reduces the steric repulsion of the flagpole hydrogens
half-chair conformation
the unstable conformation halfway between the chair conformation and the boat conformation .part of the ring is flat in the half-chair conformation.
constitutional isomers
(structural isomers) Isomers who’s atoms are connected differently: they differ in their bonding sequence.
cracking
heating large alkanes to cleave them into smaller molecules
catalytic cracking
cracking the presence of catalyst
hydrocracking
catalyst cracking the the presences of hydrogen to give mixtures an alkanes
cyclic
congaing of ring of atoms
cycloalkane
an alkane containing a ring of carbon atoms: general formula : CnH2n
degree of alkyl substitution
the number of alkyl groups bonded to a carbon atom in a compound or in an alkyl group
Primary degree
“H
“|
R–C–H
“|
“H
Secondary degree
“`H
“`|
R–C–H
“` |
“`R
Tertiary Degree
“`H
“`|
R–C–R
“`|
“`R
Quaternary Degree
“`R
“`|
R–C–R
“|
“R
1,3 -diaxial interaction
the strong steric strain between two axial groups on cyclohexane carbons with one carbon between them
dihedral angle
the angle between two specified groups in a newman project
eclipsed conformation
any conformation with bonds directly lined up with each other , one behind the other, in the Newman project. The conformation with 0= zero degrees in an eclipsed conformation.
equatorial bond
on of the six bonds (three up three down) on the cyclohexane ring that are directed out toward the “equator” of the ring. The equatorial bonds are shown in green in the drawing in the drawing at right
fused ring system
a molecule in which two or more rings share two adjacent carbon atoms
gauche conformation
a conformation with a 60 degree dihedral angle between the largest groups
geometric isomers
Compounds that have the same covalent partnershipds, but differ in spatial arrangements
halogenation
the reaction of alkanes with halogens, in the presence of heat or light, to give products with halogens atoms substituted for hydrogen atoms
Formula for halogenation
R-H+X2 when added heat or light transforms to R-X+XH
x= F, Cl, Br
heat of combustion
the heat given off when a mole of a compound is burned with excess oxygen to give CO2 and H20 in a bomb calorimeter. A measure of the energy content of a molecule.
homologs
two compounds that differ only by one or more -CH2- groups
hydrophilic
attracted to water: soluble in water
hydrophobic
repelled by water : insoluble in water
IUPAC Names
the systematic names that follow the rules adopted by the International Union Of Pure and Applies Chemistry
kerosene
A thin, volatile oil distilled from petroleum, with a boiling range higher than that of gasoline and
lower than that of diesel fuel. Kerosene was once used in lanterns and heaters, but now most of
this petroleum fraction is further refined for use as jet fuel
methane hydrate
An ice-like substance consisting of individual methane molecules trapped inside cages of water
molecules.
methine group
The- CH-group.
methylene group
The -CH2- group.
methyl group
The -CH3- group.
n-alkane, normal alkane,
or straight-chain alkane
An alkane with all its carbon atoms in a single chain, with no branching or alkyl substituents.
Newman projections
a way of drawing the conformations of a molecule by looking straight down the bond connecting two carbon atoms
octane number
A rating of the antiknock properties of a gasoline blend. Its octane number is the percentage of
isooctane (2,2,4-trimethylpentane) in an isooctane/heptane blend that begins to knock at the
same compression ratio as the gasoline being tested.
paraffins
Another term for alkanes.
ring strain
The extra strain associated with the cyclic structure of a compound, as compared with a similar
acyclic compound; composed of angle strain and torsional strain.
angle strain or Baeyer strain:
The strain associated with distorting bond angles to smaller (or larger) angles
torsional strain:
The strain associated with eclipsing of bonds in the ring.
saturated
Having no double or triple bonds.
sawhorse structures
A way of picturing conformations by looking down at an angle toward the carbon-carbon bond
skew conformation
Any conformation that is not precisely staggered or eclipsed.
spirocyclic compounds
Bicyclic compounds in which the two rings share only one carbon atom.
staggered conformation
Any conformation with the bonds equally spaced in the Newman projection. The conformation
with 0= 60 degrees is a staggered conformation.
steric strain
The interference between two bulky groups that are so close together that their electron clouds
experience a repulsion
substituent
A side chain or appendage on the main chain.
systematic names
Same as IUPAC names, the names that follow the rules adopted by the International Union of Pure
and Applied Chemistry. (
torsional energy
or conformational energy
The energy required to twist a bond into a specific conformation.
torsional strain
The resistance to twisting about a bond.
totally eclipsed conformation
A conformation with a 0 dihedral angle between the largest groups. Usually the highest-energy
conformation
Using the general molecular formula for alkanes:
(a) Predict the molecular formula of the straight-chain alkane
) Predict the molecular formula of 4,6-diethyl-12-(3,5-dimethyloctyl)triacontane, an
alkane containing 44 carbon atoms.
Write structures for the following compounds
(a) 3-ethyl-4-methylhexane
(b) 3-ethyl-5-isobutyl-3-methylnonane

(c) 4-tert-butyl-2-methylheptane
(d) 5-isopropyl-3,3,4-trimethyloctane

Provide IUPAC names for compounds.
All of the following names are incorrect or incomplete. In each case, draw the structure (or a
possible structure) and name it correctly
(a) 2-methylethylpentane
(b) 2-ethyl-3-methylpentane
(c) 3-dimethylhexane
(d) 4-isobutylheptane
(e) 2-bromo-3-ethylbutane
(f) 2-diethyl-3-methylhexane
Give structures and names for:
a) the five isomers of C6H14
(b) the nine isomers of C7H16
Draw the structures of the following groups, and give their more common names.
(a) the (1-methylethyl) group (b) the (2-methylpropyl) group
(c) the (1-methylpropyl) group (d) the (1,1-dimethylethyl) group
(e) the (3-methylbutyl) group, sometimes called the “isoamyl” group
Draw the structures of the following compounds.
(a) 4-(1,1-dimethylethyl)octane (b) 5-(1,2,2-trimethylpropyl)nonane
(c) 3,3-diethyl-4-(2,2-dimethylpropyl)octane
Without looking at the structures, give molecular formulas for the compounds Use the names of the groups to determine the number of carbon atoms, then use the
12n+22 rule.
(a) 4-(1,1-dimethylethyl)octane (b) 5-(1,2,2-trimethylpropyl)nonane
List each set of compounds in order of increasing boiling point. hexane, octane, and decane
List each set of compounds in order of increasing boiling point.
octane, and (CH3) 3C-C(CH3)3C and CH3CH2C(CH3)2CH2CH2CH3
Draw a graph, similar to Figure 3-9, of the torsional strain of 2-methylpropane as it rotates about
the bond between C1 and C2. Show the dihedral angle and draw a Newman projection for
each staggered and eclipsed conformation.
Draw a graph, similar to Figure 3-11, of the torsional energy of 2-methylbutane as it rotates
about the bond.
Draw a perspective representation of the most stable conformation of 3-methylhexane
Draw the structure and give the molecular formula for each of the following compounds.
(a) 1-ethyl-3-methylcycloheptane (b) isobutylcyclohexane
(c) cyclopropylcyclopentane (d) 3-ethyl-1,1-dimethylcyclohexane
(e) 3-ethyl-2,4-dimethylhexane (f) 1,1-diethyl-4-(3,3-dimethylbutyl)cyclohexane
Which of the following cycloalkanes are capable of geometric (cis-trans) isomerism? Draw the
cis and trans isomers.
(a) 3-ethyl-1,1-dimethylcyclohexane
(b) 1-ethyl-3-methylcycloheptane
(c) 1-ethyl-3-methylcyclopentane
(d) 1-cyclopropyl-2-methylcyclohexane
The heat of combustion of cis-1,2-dimethylcyclopropane is larger than that of the trans isomer.
Which isomer is more stable? Use drawings to explain this difference in stability.
trans-1,2-Dimethylcyclobutane is more stable than cis-1,2-dimethylcyclobutane, but cis-1,3-
dimethylcyclobutane is more stable than trans-1,3-dimethylcyclobutane. Use drawings to
explain these observations.
The cyclohexane chair just drawn has the headrest to the left and the footrest to the right. Draw
a cyclohexane chair with its axial and equatorial bonds, having the headrest to the right and
the footrest to the left.
Draw 1,2,3,4,5,6-hexamethylcyclohexane with all the methyl groups
(a) in axial positions. (b) in equatorial positions
Draw a Newman projection, similar to Figure 3-25, down the bond in the equatorial
conformation of methylcyclohexane. Show that the equatorial methyl group is also anti to C5.
(Using your models will help.)
Draw a Newman projection, similar to Figure 3-25, down the bond in the equatorial
conformation of methylcyclohexane. Show that the equatorial methyl group is also anti to C5.
(Using your models will help.)
Draw the most stable conformation of:
(a) ethylcyclohexane (b) 3-isopropyl-1,1-dimethylcyclohexane
(c) cis-1-tert-butyl-4-isopropylcyclohexane
(a) Draw both chair conformations of cis-1,2-dimethylcyclohexane, and determine which
conformer is more stable.
(b) Repeat for the trans isomer.
(c) Predict which isomer (cis or trans) is more stable.
(a) Draw both chair conformations of cis-1,4-dimethylcyclohexane, and determine which
conformer is more stable.
(b) Repeat for the trans isomer.
(c) Predict which isomer (cis or trans) is more stable.
Use your results from Problem 3-25 to complete the following table. Each entry shows the
positions of two groups arranged as shown. For example, two groups that are trans on adjacent
carbons (trans-1,2) must be both equatorial (e,e) or both axial (a,a).
Draw the most stable conformation of trans-1-ethyl-3-methylcyclohexane.
Draw the two chair conformations of each of the following substituted cyclohexanes. In each
case, label the more stable conformation
(a) cis-1-ethyl-2-methylcyclohexane
(b) trans-1,2-diethylcyclohexane
(c) cis-1-ethyl-4-isopropylcyclohexane
(d) trans-1-ethyl-4-methylcyclohexane
Name the following compounds. Remember that two up bonds are cis; two down bonds are cis;
one up bond and one down bond are trans.
Draw the most stable conformation of
(a) cis-1-tert-butyl-3-ethylcyclohexane
(b) trans-1-tert-butyl-2-methylcyclohexane
(c) trans-1-tert-butyl-3-(1,1-dimethylpropyl)cyclohexane
Given the IUPAC name or common name of an alkane, draw the structure and give the molecular formula
Explain and predict trends in the physical properties of alkanes.
Use Newman projections to compare conformational energies and predict the most
stable conformation. Show how the torsional energy varies as the dihedral angle
changes
Use Newman projections to compare conformational energies and predict the most
stable conformation. Show how the torsional energy varies as the dihedral angle
changes
Identify and draw cis and trans stereoisomers of disubstituted cycloalkanes.
Identify and draw cis and trans stereoisomers of disubstituted cycloalkanes.
There are eighteen isomeric alkanes of molecular formula C8H18. Draw and name any eight of them
Draw and name the six isomeric cyclopentanes of molecular formula . These will include four constitutional
isomers, of which two show geometric (cis-trans) stereoisomerism
Which of the following structures represent the same compound? Which ones represent different compounds?
Name the structures given in Problem 3-33, parts (a), (c), (e), and (f). Make sure that your names are the same for
structures that are the same, and different for structures that are different.
Draw the structure that corresponds with each name.
(a) 3-ethyloctane (b) 4-isopropyldecane (c) sec-butylcycloheptane
(d) 2,3-dimethyl-4-propylnonane (e) 2,2,4,4-tetramethylhexane (f) trans-1,3-diethylcyclopentane
(g) cis-1-ethyl-4-methylcyclohexane (h) isobutylcyclopentane (i) tert-butylcyclohexane
(j) pentylcyclohexane (k) cyclobutylcyclohexane (l) cis-1-bromo-3-chlorocyclohexane
Each of the following descriptions applies to more than one alkane. In each case, draw and name two structures that match
the description.
(a) an isopropylheptane (b) a diethyldecane (c) a cis-diethylcyclohexane
(d) a trans-dihalocyclopentane (e) a (2,3-dimethylpentyl)cycloalkane (f) a bicyclononane
Write structures for a homologous series of alcohols having from one to six carbons.
The following names are all incorrect or incomplete, but they represent real structures. Draw each structure and name it
correctly.
(a) 2-ethylpentane
(b) 3-isopropylhexane
(c) 5-chloro-4-methylhexane
(d) 2-dimethylbutane
(e) 2-cyclohexylbutane (f) 2,3-diethylcyclopentane
In each pair of compounds, which compound has the higher boiling point? Explain your reasoning
(a) octane or 2,2,3-trimethylpentane (b) nonane or 2-methylheptane (c) 2,2,5-trimethylhexane or nonane
There are eight different five-carbon alkyl groups
(a) Draw them.
(b) Give them systematic names.
(c) In each case, label the degree of substitution (primary, secondary, or tertiary) of the head carbon atom, bonded to the
main chain.
Use a Newman projection, about the indicated bond, to draw the most stable conformer for each compound.
(a) 3-methylpentane about the bond
b) 3,3-dimethylhexane about the bond
Draw the two chair conformations of cis-1,3-dimethylcyclohexane and label all the positions as axial or equatorial
(b) Label the higher-energy conformation and the lower-energy conformation.
(c) The energy difference in these two conformations has been measured to be about 23 kJ (5.4 kcal) per mole. How
much of this energy difference is due to the torsional energy of gauche relationships?
(d) How much energy is due to the additional steric strain of the 1,3-diaxial interaction?
raw the two chair conformations of each compound and label the substituents as axial and equatorial. In each case, determine which conformation is more stable
(a) cis-1-ethyl-2-isopropylcyclohexane
(b) trans-1-ethyl-2-isopropylcyclohexane
(c) cis-1-ethyl-3-methylcyclohexane
(d) trans-1-ethyl-3-methylcyclohexane
(e) cis-1-ethyl-4-methylcyclohexane
(f) trans-1-ethyl-4-methylcyclohexane
using what you know about the informational energies of substituted cyclohexanes, predit which of th two decal in isomers is more stable. Explain your reason
Convert each Newman projection to the equivalent line-angle formula, and assign the IUPAC name.
Draw Newman projections along the bond to show the most stable and least stable conformations of 3-ethyl-
2,4,4-trimethylheptane
Conformational studies on ethane-1,2-diol ( ) have shown the most stable conformation about the central c-c
bond to be the gauche conformation, which is 9.6 kJ/mol (2.3 kcal/mol) more stable than the anti conformation.
Draw Newman projections of these conformers and explain this curious result.
The most stable form of the common sugar glucose contains a six-membered ring in the chair conformation with all the
substituents equatorial. Draw this most stable conformation of glucose.
Determine whether the following objects are chiral or achiral.
roll of duck tape
can opener
snow sled
wind bottle cork screw
wooden student chain
salt shaker
metal spoon
rifle
knotted rope
Make a model and draw a three dimensional structure for each compound. Then draw the mirror image of your original structure and determine whether the mirror image is the same compound. Label each structure as being chiral or archiral and label of enantiomers
(a) cis-1,2-dimethylcyclobutane
(b) trans-1,2-dimethylcyclobutane
(c) cis- and trans-1,3-dimethylcyclobutane
(d) 2-bromobutane
Identify each asymmetric carbon atom in the following structure:
Identify each asymmetric carbon atom in the following structure:
Draw the enantiomers of 1,3-dibromobutane and label them as (R) and (S). (Making a model
is particularly helpful for this type of problem.
When one of the enantiomers of butan-2-ol is placed in a polarimeter, the observed rotation is
4.05° counterclockwise. The solution was made by diluting 6.00 g of butan-2-ol to a total of
40.0 mL, and the solution was placed into a 200-mm polarimeter tube for the measurement.
Determine the specific rotation for this enantiomer of butan-2-ol.
Since it is levorotatory, this must be The concentration is 6.00 g per
and the path length is The specific rotation
is -13.5°.
[a]D
25 = -4.05°
10.150212.002 = -13.5°
40.0 mL = 0.150 g>mL, 200 mm = 2
A solution of 2.0 g of in 10.0 mL of water
was placed in a 100-mm cell. Using the sodium D line, a rotation of was found at
25 °C. Determine the specific rotation of 1+2-glyceraldehyde.
A chiral sample pair give a rotation the is close to 180 degrees. How can one tell the weather this rotation is + 180 degrees or – 180 degrees
If you had the two enantiomers of carvone in unmarked bottles, could you use just your nose
and a polarimeter to determine:
(a) whether it is the or enantiomer that smells like spearmint?
(b) whether it is the (R) or (S) enantiomer that smells like spearmint?
(c) With the information given in the drawings of carvone above, what can you add to your
answers to (a) or (b)?
Calculate the e.e. and the specific rotation of a mixture containing 6.0 g of
and 4.0 g of
(-) – butan-2ol
SOLUTION
In this mixture, there is a 2.0 g excess of the isomer and a total of 10.0 g, for an e.e. of 20%.
We can envision this mixture as 80% racemic [4.0 g and 4.0 g ] and 20% pure
The specific rotation of enantiomerically pure is . The rotation of this
mixture is
= 1+13.5°2 * 120%2 = +2.7°
observed rotation = 1rotation of pure enantiomer2 * 1o.p.2
1+2-butan-2-ol +13.5°
o.p. = e.e. = ƒ6.0 – 4.0ƒ
6.0 + 4.0 = 2.0
10.0 = 20%
(+) (-) (+).
(+)
1-2-butan-2-ol.
1+2-butan-2-ol
A chemist finds that the addition of to the catalytic reduction of butan-2-one
(Figure 5-16) gives a product that is slightly optically active, with a specific rotation of
Calculate the percentages of and formed in this reaction. 1+2-butan-2-ol 1-2-butan-2-ol
+0.45°.
Draw each compound in its most stable conformation(s). Then draw it in its most symmetric
conformation, and determine whether it is capable of showing optical activity.
(a) 2-methylbutane
(b) trans-1,2-dibromocyclohexane
Make a model of each compound, draw it in its most symmetric conformation, and
determine whether it is capable of showing optical activity
(a) 1-bromo-1-chloroethane (b) 1-bromo-2-chloroethane
(c) 1,2-dichloropropane
(d) cis-1,3-dibromocyclohexane
(e) trans-1,3-dibromocyclohexane
(f) trans-1,4-dibromocyclohexane
Star each asymmetric carbon atom, label each as (R) or (S), and compare your result
from part (1) with the prediction you would make based on the asymmetric carbons.
Draw all the stereoisomers of a given structure, and identify the relationships
between the stereoisomers.
Classify molecules as chiral or achiral, and draw their mirror images. Identify and
draw any mirror planes of symmetry
Identify asymmetric carbon atoms, and name them using the (R) and (S) nomenclature.
Calculate specific rotations from polarimetry data, and use specific rotations to
determine the optical purity and the enantiomeric excess of mixtures.
Use Fischer projections to represent the stereochemistry of compounds with one or
more asymmetric carbon atoms.
Identify pairs of enantiomers, diastereomers, and meso compounds, and explain
how they differ in their physical and chemical properties.
Explain how different types of stereoisomers can be separated.
absolute configuration
The detailed stereochemical picture of a molecule, including how the atoms are arranged in
space. Alternatively, the (R) or (S) configuration at each asymmetric carbon atom.
achiral
achiral Not chiral.
allenes
Compounds having two double bonds that meet at a single carbon atom, C=C=C
The two outer carbon atoms are trigonal planar, with their planes perpendicular to each other.
Many substituted allenes are chiral.
asymmetric carbon atom
(chiral carbon atom) A carbon atom that is bonded to four different groups
Cahn-Ingold-Prelog convention
The accepted method for designating the absolute configuration of a chirality center (usually an
asymmetric carbon) as either (R) or (S).
chiral
Different from its mirror image.
chiral carbon atom
asymmetric carbon atom) A carbon atom that is bonded to four different groups.
chirality center
the IUPAC term for an atom holding a set of ligands in a spatial arrangement that is not superimposable on its mirror image
chiral probe
A molecule or an object that is chiral and can use its own chirality to differentiate between
mirror images. (
cis
On the same side of a ring or double bond.
cis-trans isomers
(geometric isomers) Isomers that differ in their geometric arrangement on a ring or double bond;
cis-trans isomers are a subclass of diastereomers
configurations
The two possible spatial arrangements around a chirality center or other stereocenter.
configurational isomers
(see stereoisomers)
conformers
(conformational isomers) Structures that differ only by rotations about single bonds. In most
cases, conformers interconvert at room temperature; thus, they are not different compounds and
not true isomers
constitutional isomers
(structural isomers) Isomers that differ in the order in which their atoms are bonded together.
D-L configurations
(Fischer- Rosanoff convention) D has the same relative configuration at (=) – glyceraldehyde. L as the same relative configuration as (-)
dextrorotatory, or (d)
Rotating the plane of polarized light clockwise.
dextrorotatory, (+) or (d)
Rotating the plane of polarized light clockwise.
diastereomers
Stereoisomers that are not mirror images.
enantiomeric excess (e.e.)
The excess of lone enatiomer in a mixture of enantiomer expressed as a percentage of the mixture. Similar to optical purity
enantiomers
A pair of nonsuperimposable mirror-image molecules: mirror-image isomers.
Fischer projection
A method for drawing an asymmetric carbon atom as a cross. The carbon chain is kept along the
vertical, with the IUPAC numbering from top to bottom. Vertical bonds project away from the
viewer, and horizontal bonds project toward the viewer.
geometric isomers
(see cis-trans isomers)
internal mirror plane
A plane of symmetry through the middle of a molecule, dividing the molecule into two
mirror-image halves. A molecule with an internal mirror plane of symmetry cannot be
chiral
isomers
Different compounds with the same molecular formula.
Leftorium
An imaginary store that sells the enantiomers of everyday chiral objects such as scissors, rifles,
can openers, etc
levorotatory, or (l)
Rotating the plane of polarized light counterclockwise.
meso compound
An achiral compound that contains chirality centers (usually asymmetric carbon atoms).
Originally, an achiral compound that has chiral diastereomers.
optical isomers
(archaic; see enantiomers) Compounds with identical properties except for the direction in
which they rotate polarized light.
optical activity
Rotation of the plane of polarized light.
optically active
Capable of rotating the plane of polarized light
optical purity (o.p.)
the specific rotation of a mixture of two enantiomers, expressed as a percentage of the specific rotation of one of the pure enantiomers. similar to enantiomeric excess.
plane-polarized light
Light composed of waves that vibrate in only one plane.
polarimeter
An instrument that measures the rotation of plane-polarized light by an optically active
compound. (
racemic mixture
a mixture of equal quants of enantiomers , such that the mixtures is optically inactive
relative configuration
The experimentally determined relationship between the configurations of two molecules, even
though the absolute configuration of either may not be known.
resolution
stereocenter
resolving agent
A chiral compound (or chiral material on a chromatographic column) used for separating
enantiomers.
2 ” rule
A molecule with n chiral carbon atoms might have as many as stereoisomers.
specific rotation
A measure of a compound’s ability to rotate the plane of polarized light, given bywhere c is concentration in g mL and l is length of sample cell (path length) in decimeters
stereocenter
(stereogenic atom) An atom that gives rise to stereoisomers when its groups are interchanged.
Asymmetric carbon atoms and double-bonded carbons in cis-trans alkenes are the most common
stereocenters.
stereochemistry
The study of the three-dimensional structure of molecules
stereoisomers
The study of the three-dimensional structure of molecules
structural isomers
(see constitutional isomers) Isomers that differ in the order in which their atoms are bonded
together.
superimposable
(see constitutional isomers) Isomers that differ in the order in which their atoms are bonded
together.
trans
On opposite sides of a ring or double bond.
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