achiral:
A molecule that's superimposable
on its mir ror image. Achiral
molecules do not rotate plane-polarized light.
acid: A proton donor or an electron pair
acceptor.
alcohol: A molecule containing a hydroxyl (OH)
group. Also a functional group.
aldehyde:
A molecule containing a terminal carbonyl (CHO) group. Also
a functional group.
alkane:A
molecule containing only C-H and C-C single bonds.
alkene:A
molecule containing one or more carbon-carbon double bonds.
Also a functional group.
alkyne:A
molecule containing one or more carbon-carbon triple bonds.
Also a functional group.
allylic
carbon: An sp3
carbon adjacent to a double bond.
amide:
A molecule containing a carbonyl group attached to a nitrogen
(-CONR2). Also a functional group.
amine:
A molecule containing an isolated nitrogen = (NR3).
Also a functional group.
anion:
A negatively charged atom or molecule.
anti
addition: A reaction in which th= e two groups of a reagent
X-Y add on opposite faces of a carbon-carbon bond.
anti
conformation: A type of staggered conformation in which
the two big groups are opposite of each other in a Newman
projection.
anti-aromatic:
A highly unstable planar ring system with 4n
pi electrons.
anti-periplanar
(a.k.a. anticoplanar): The conformation in which a hydrogen
and a leaving group are in the same plane and on opposite
sides of a carbon-carbon single bond. The conformation required
for E2 elimination.
aprotic
solvents: Solvents that do not contain O-H or N-H bonds.
aromatic:
A planar ring system that contains uninterrupted p orbitals
around the ring and a total of 4n+2
pi electrons. Aromatic compounds are unusually stable compounds.
aryl:
An aromatic group as a substituent.
axial
bond: A bond perpendicular to the equator of the ring
(up or down), typically in a chair cyclohexane.
base:
A proton acceptor or an electron pair donor.
benzyl
group: A benzene ring plus a methylene (CH2)
unit (C6H5—CH2).
benzylic
position: The position of a carbon attached to a benzene
ring.
benzyne:
A highly reactive intermediate. A benzene ring with a
triple bond.
bicyclic:
A molecule with two rings that share at least two carbons.
Brønsted
acid: A proton donor.
Brønsted
base: A proton acceptor.
carbanion:
A negatively charged carbon atom.
carbene:
A reactive intermediate, characterized by a neutral, electron-deficient
carbon center with two substituents (R2C:).
carbocation:
A positively charged carbon.
carbonyl
group: A carbon double bonded to oxygen (C=O).
carboxylic
acid:A molecule containing a carboxyl (COOH) group.Also
a functional group.
cation:
A positively charged molecule or atom.
chair
conformation: Typically,
the most stable cyclohexane conformation. Looks like a chair.
chemical
shift: The location of an
NMR peak relative to the standard tetramethylsilane (TMS),
given in units of parts per million (ppm).
chiral
center: A carbon or other atom
with four nonidentical substituents.
chiral
molecule: A molecule that's not superimposable
on its mirror image. Chiral molecules
rotate plane-polarized light.
cis:
Two identical substituents on
the same side of a double bond or ring.
configuration:
The three-dimensional orientation of atoms around a chiral
center. It’s given the designation R or S.
conformation:
The instantaneous spatial arrangements of atoms. Conformations
can change by rotation around single bonds.
conjugate
acid: The acid that results from protonation of a base.
conjugate
base: The base that results from the deprotonation of an acid.
conjugated
double bonds: Double bonds separated by one carbon-carbon
single bond. Alternating double bonds.
constitutional
isomers: Molecules with the same molecular formula but
with atoms attached in different ways.
coupling
protons: Protons that interact with each other and split
the NMR peak into a certain number of lines following the
n+1 rule.
coupling
constant: The distance between two neighboring lines in
an NMR peak (given in units of Hz).
covalent
bond: Bond in which the two electrons are shared between
the two atoms.
dehydrohalogenation:
Loss of a hydrohalic acid
(like HBr, HCl, and so on) to
form a double bond.
delta
value (a.k.a. d
value): The chemical shift.
The location of an NMR peak relative to the standard
tetramethylsilane (TMS), given
in units of parts per million (ppm).
diastereomers:
Stereoisomers that are not
mirror images of each other.
Diels-Alder
reaction: A reaction that brings together a diene
and a dienophile to form bicyclic
molecules and rings.
diene:
A molecule that contains two alternating double bonds. A reactant in the
Diels-Alder reaction.
dienophile:
A reactant in
the Diels-Alder reaction that contains a double bond.
Dienophiles are often substituted
with electron-withdrawing groups.
dipole
moment: A measure of the separation of charge in a bond
or molecule.
doublet:
Describes an NMR signal split into two peaks.
eclipsed
conformation: Conformation about a carbon-carbon single
bond in which all of the bonds off of two adjacent carbons
are aligned with each other (0o apart when viewed
in a Newman projection).
E
isomer: Stereoisomer in which the two highest priority
groups are on opposite sides= of a ring or double bond.
E1
elimination reaction: A reaction that eliminates a hydrohalic
acid (like HCl, HBr,
etc) to form an alkene. A first order reaction that goes through a
carbocation mechanism.
E2
elimination reaction: A reaction that eliminates a hydrohalic
acid (like HCl, HBr,
etc) to form an alkene. A second order reaction that occurs in single step, in which the
double bond is formed as the hydrohalic
acid is eliminated.
electronegativity:
A term describing the electron piggishness
of an atom. More technically, a measure
of the tendency of an atom to attract the electrons in a covalent
bond to itself.
electrophile:
Electron lover. A molecule that can
accept a lone pair of electrons (a Lewis acid).
enantiomers:
Molecules that are nonsuperimposable
mirror ima= ges of each other.
equatorial:
The bonds in a chair cyclohexane that are oriented along the equator of the ring.
ester:
A molecule containing a carbonyl group adjacent to an
oxygen (RCOOR'). Also a functional group.
ether:
A molecule containing oxygen singly-bonded to two carbon
atoms. Also a functional group. Ether often refers to diethyl ether.
fingerprint
region: Region of an IR spectrum below 1,500 cm-1.
The fingerprint region of the IR spectrum is often complex
and difficult to interpret.
functional
group: A reactivity center.
gauche
conformation: A type of staggered conformation in which
two big groups are next to each other
halide:
A member of the VIIA column of the periodic table (like
F, Cl, Br, I, etc). Or a molecule that
contains one of these atoms.
Also a functional group.
Hückel's
rule: A rule that states that completely conjugated planar
rings with 4n+2
pi electrons are aromatic.
hybrid
orbitals: Orbitals formed from mixing together atomic orbitals, like the spx orbitals, which result from mixing s and p orbitals.
hyperconjugation:
Weak interaction (electron donation) between sigma bonds
with p orbitals. Hyperconjugation explains why alkyl substituents stabilize carbocations.
inductive
effects: Electron donation or withdrawal by electropositive
or electronegative atoms through the sigma bond framework.
intermediate:
Any species formed in a reaction on the way to making
the product. Typically, intermediates are unstable.
ionic
bond: Bond in which the electrons are unshared between
two atoms.
IR
spectrosco py: An instrumental technique that measures
IR light absorption by molecules. Can be used to determine
functional groups in an unknown molecule.
isolated
double bonds: Double bonds separated by more than one
carbon-carbon single bond.
J
value: The coupling constant between two peaks in an NMR
signal. Given in units of Hz.
ketone:
A compound that contains a carbonyl group attached to two
carbons. Also a functional group.
kinetic
product: The
product that forms the fastest. (This product has the lowest
energy of activation.)
kinetics:
The study of
reaction rates.
Lewis
acid:An electron
pair acceptor.
Lewis
base:An electron
pair donor.
Markovniknov’s
rule: A rule that
states that electrophiles add to the less highly substituted
carbon of a carbon-carbon double bond (or the carbon with
the most hydrogen atoms).
mass
spectrometry: An instrumental technique involving the
ionization of molecules into fragments. Can be used to determine
the molecular weights of unknown molecules.
meso
compounds: Molecules that have chiral
centers but are achiral as a result of one or more planes of symmetry in
the molecule.
meta:
Describes the positions of two substituents on a benzene ring that are separated by one
carbon.
meta-directing
substituent: Any substituent
on an aromatic ring that directs in coming electrophiles to
the meta position.
molecular
ion: The fragment in a mass spectrum that corresponds
to the cation radical (M+)of the molecule. The molecular ion
gives the molecular mass of the molecule.
molecular
orbital theory: Model for depict ing the location of electrons
that allows electrons to delocalize across the entire molecule.
A more accurate but less user-friendly theory than the valence-bond
model.
multistep
synthesis: Synthesis of a compound that takes several
steps to achieve.
n+1
rule: Rule for predicting the coupling for a proton =
in 1H NMR spectroscopy. An NMR signal will split
into n+1 peaks, where n is the number of equivalent adjacent
protons.
natural
product: A compound produced by a living organism.
nitrile:
A compound contain a cyano group: a carbon triply-bonded
to a nitrogen (CN). Also a functional group
NMR:
Nuclear magnetic resonance sprectroscopy. A technique
th at measures radiofrequency light absorption by molecules.
A powerful structure-determining method.
node:
A region in an orbital with zero electron density.
nucleophile:
Nucleus lover. A molecule with the ability to donate a
lone pair of electrons (a Lewis base)
nucleophilicity:
A measure of the reactivity of a nucleophile in a nucleophilic
substitution reaction.
organic
compound: Carbon-containing compound.
optically
active: Rotates plane-polarized light.
orbital:
The region of space in which an electron is confined (the
electron “apartment”).
ortho:
Describes the positions of two substituents on a benzene
ring that are on adjacent carbons.
ortho-para
director: An aromatic substituent
that directs incoming electrophiles to the ortho or para positions.
para:
Describes the poitions of
two substituents on a benzene ring that are separated by two
carbons.
phenyl
ring: A benzene ring as
a substituent. Abbreviated Ph.
pi
bond (a.k.a. p bond): A
bond with electron density above and below the two atoms,
but not directly between the two atoms. Found in double and
triple bonds.
pKa:The
scale for defining a molecule's acidity (pKa =-log Ka).
plane-polarized
light: Light that oscillates
in a single plane.
plane
of symmetry: A plane cutting
through a molecule in which both halves are mirror images
of each other.
protic
solvent: A solvent that
contains O-H or N-H bonds.
proton:
An H+ ion. Also
a positively-charged nuclear particle.
R
group: Abbreviation given
to an unimportant part of a molecule. Indicates Rest
of molecule.
racemic
mixture: A 50:50 mixture
of two enantiomers. Racemic mixtures are optically inactive
(don't rotate plane-polarized light).
radical:
An atom or molecule with an unpaired electron.
resonance
structures: Structures used to better depict the location
of pi and nonbonding electrons on a molecule. A molecule looks
like a hybrid of all resonance structures.
s-cis
conformation: A conformation in which the two double
bonds of a conjugated diene are on the same side of the carbon-carbon
single bond that connects them. The required conformation
for the Diels-Alder reaction.
s-trans
conformation: The conformation in which the two double
bonds of a conjugated diene are on opposite sided of the carbon-carbon
single bond that connects them.
sigma
bond (a.k.a. s bond): A bond in which electrons are located
between the nuclei of the bonding atoms. Single bonds
are sigma bonds.
singlet:
Describes an NMR signal consisting of only one peak.
SN1
reaction: A first order substitution reaction that goes
through a carbocation intermediate.
SN2
reaction: A second order substitution reaction that takes
place in one step and has no intermediates.
sp:
A hybrid orbital made by mixing one s orbital and one
p orbital.
sp2:
A hybrid orbital made by mixing one s orbital and two
p orbitals.
sp3:
A hybrid orbital made by mixing one s orbital and three
p orbitals.
staggered
conformation: Conformation about a carbon-carbon single
bond in which bonds off of one carbon are at a maximum distance
apart from bonds coming off of an adjacent carbon (60odg
apart when viewed in a Newman projection).
stereochemistry:
Study of molecules in three dimensions.
stereoisomers:
Molecules that have the same atom connectivity, but different
orientations = of those atoms in three-dimensional space.
steric
hindrance: Term referring to the way that atoms can shield
a site by getting in the way of approach of a reactant.
substituent:
A piece that sticks off of the main carbon chain or ring.
syn
addition: A reaction in which two groups of a reagent
X-Y add on the same face of a carbon-carbon double bond.
tautomers:
Molecules that differ in the placement of a hydrogen and double
bonds and are easily interconvertible. Keto and enol forms
are tautomers.
thermodynamics:
Study of the energies of molecules.
thermodynamic
product: The reaction product with the lowest energy..
thiol:A
molecule containing an SH group. Also a functional group.
transition
state: The highest
point on the energy hill that takes one species into another.
triplet:
Describes an
NMR signal split into three peaks.
Z
isomer: Isomer
in which the two highest-priority substituents are on the
same side of a double bond or ring.
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