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Test 3
Ch 9-12
77
Chemistry
Undergraduate 3
04/08/2009

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Term
Valence bond theory
Definition
tied to Lewis's idea of bonding electron pairs between atoms and lone pairs of electrons localized on a particular atom
Term
molecular orbital theory
Definition
derives molecular orbitals that are spread out (delocalized) over the molecule by combining atomic orbitals to form a set of orbitals that are the property of the molecule, and then distribute the electrons of the molecule w/in these orbitals
Term
orbital overlap
Definition
increases the probability of finding the bonding electrons in the region of space b/w the two nuclei
Term
sigma bond
Definition
covalent bond from the overlap of two s orbitals, one from each of two atoms. the electron density is greatest slong the axis of the bond
Term
orbital hybridization
Definition
a new set of orbitals (hybrid orbitals) can be created by mixing the s, p, and d atomic orbitals on an atom. # hybrid orbitals = # mixed atomic orbitals. hybrid orbital sets are built by combining an s orbital with as many p orbitals (and d orbitals if necessary) to have enough hybrid orbitals to accommodate the bond and lone pairs on the central atom. the hybrid orbitals are directed toward the terminal atoms, leading to better orbital overlap and stronger bond b/w the central and terminal atoms
Term
choosing hybridization
Definition
hybrid orbitals required by an atom in a molecule or ion are chosen to match the electron pair geometry of the atom b/c a hybrid orbital is required for each sigma bond electron air and each lone pair
Term
types of hybridization: sp
Definition
if the valence shell s orbital on the central atom in a molecule or ion is mixed with a valence shell p orbital on that same atom, two sp hybrid orbitals are created and separated by 180 degrees
Term
types of hybridization: sp^2
Definition
if an s orbital is combined with two p orbitals, all in the same valence shell, three sp^2 hybrid orbitals are created, in the same plane separated by 120 degrees
Term
types of hybridization: sp^3
Definition
when the s orbital in a valence shell is combined with three p orbitals, the result is four hybrid orbitals, each labeled sp^3, separated by 109.5 degrees (tetrahedral)
Term
types of hybridization: sp^3d and sp^3d^2
Definition
if one or two d orbitals are combined with s and p orbitals in the same valence shell, two other hybrid orbital sets are created. these are utilized by the central atom of a molecule or ion with a trigonal-bipyramidal or octahedral electron-pair geometry
Term
pi bond
Definition
the overlap region is above and below the internuclear axis, and the electron density is above and below the bond axis
Term
forming pi bonds
Definition
can form only if (a) there are unhybridized p orbitals on adjacent atoms and (b) the p orbitals are perpendicular to the plane of the molecule and parallel to one another
Term
isomer
Definition
compound that has the same formula but different structure
Term
bonding molecular orbital
Definition
molecular orbital in which the energy of the electrons is lower than that of the parent orbital electrons (is a sigma orbital)--increased probability that electrons will reside in the bond region b/w the two nuclei
Term
antibonding molecular orbital
Definition
molecular orbital in which the energy of the electrons is higher than that of the parent orbital electrons (is a sigma orbital)--decreased probability that electrons will reside in the bond region b/w the two nuclei, so the nuclei repel one another. system is destabalized b/c energy of system is higher than that of the atoms themselves
Term
bond order
Definition
1/2 (number of electrons in bonding MOs - number of electrons in antibonding MOs)
Term
heteronuclear diatomic molecules
Definition
molecule composed of two atoms of different elements
Term
ways carbon reaches octet
Definition
1)by forming four single bonds, 2)by forming a double bond and two single bonds, 3)by forming two double bonds, 4)by forming a triple bond and a single bond
Term
structural isomers
Definition
compounds having the same elemental composition but the atoms are linked together in different ways
Term
stereoisomers
Definition
compounds with the same formula and in which there is similar attachment of atoms, where the atoms have different orientations in space. two types: geometric and optical isomers
Term
geometric isomers
Definition
isomers in which the atoms of the molecule are arranged in different geometric relationships (cis and trans)
Term
optical isomers
Definition
molecules that have nonsuperimposable mirror images
Term
chiral
Definition
molecules that have nonsuperimposable mirror images
Term
enantiomers
Definition
pairs of nonsuperimposable molecules. pure samples have same physical properties and pairs rotate polarized light to an equal extent in opposite directions
Term
hydrocarbon
Definition
compounds made of carbon and hydrogen only (subgroups: alkanes, cycloalkanes, alkenes, alkynes, aromatic compounds)
Term
alkanes
Definition
general formula CnH2n+2, often called saturated compounds (each C atoms is attached to four other atoms). as the # of C atoms in an alkane increases, the # of possible structural isomers increases
Term
alkyl groups
Definition
hydrocarbon substituents
Term
properties of alkanes
Definition
some are gases at room temp, higher molar mass compounds are liquids or solids (MP and BP increases with molar mass, representing increased forces of attraction b/w molecules). pure alkanes are colorless, gases and liquids have odors, all are insoluble in water (since they're nearly nonpolar), burn readily in air, low chemical reactivity
Term
cycloalkanes
Definition
constructed with tetrahedral carbon atoms joined together to form a ring
Term
strained hydrocarbons
Definition
C-C bonds are weaker and the molecules readily undergo ring-opening reactions that relieve the bond angle strain
Term
alkenes
Definition
hydrocarbons with 1+ C=C double bonds (double bonds add possibility of geometric isomerism and increased reactivity), general formula CnH2n
Term
alkynes
Definition
compounds with carbon-carbon triple bond, gen formula CnH2n-2
Term
properties of alkenes and alkynes
Definition
colorless, low-molar-mass compounds are gases, others are liquids or solids. unsaturated compounds. carbon atoms liked by double bond are bonded to only 3 atoms; in alkynes, are bonded to 2 atoms
Term
addition reactions
Definition
molecules with the general formula X-Y add across the carbon-carbon double bond to increase the number of groups attached to carbon. products are often substituted alkanes
Term
Markovnikov's rule
Definition
when a reagent HX adds to an unsymmetrical alkene, the hydrogen atom in the reagent becomes attached to the C that already has the lagest # of hydrogens
Term
hydrogenation
Definition
reagent added to a double bond is hydrogen (X-Y=H2)
Term
properties of aromatic compounds
Definition
colorless liquids or solids, insoluble in water, soluble in nonpolar solvents, oxidezed by O2 to form CO2 and H2O, unsaturated hydrocarbons
Term
resonance stabilization
Definition
extra stability of pi bonding
Term
functional group
Definition
an atom or group of atoms attached to a C atom in the hydrocarbon, formula written as R-X in which R is a hydrocarbon lacking a H atom, X is the functional group that replaced the H
Term
alcohol
Definition
when one of the H atoms of an alkane is replaced by a hydroxyl (-OH) group
Term
ether
Definition
any of a class of organic compounds characterized by the presence of an oxygen atom singly bonded to two carbon atoms
Term
amines
Definition
one or more H atoms of NH3 are replaced with an organic group. trigonal pyramidal structure. chategorized based on # of organic substituents as primary(one organic group), secondary(2), tertiary(3). offensive odors
Term
carbonyl group
Definition
functional group that characterizes aldehydes and ketones, consisting of a carbon atom doubly bonded to an oxygen atom
Term
aldehydes
Definition
RCHO, have an organic group (-R) and a H atom attached to a carbonyl group
Term
ketones
Definition
RCOR', have two -R groups attached to the carbonyl carbon; may be the same groups or diff groups
Term
carboxylic acids
Definition
RCO2H, have an -R group and an -OH group attached to the carbonyl carbon
Term
esters
Definition
RCO2R', have -R and -OR' groups attached to the carbonyl carbon
Term
amides
Definition
RCONR2',RCONHR',RCONH2, have an -R group and an amino group (-NH2,-NHR,-NR2) bonded to the carbonyl carbon
Term
primary alcohols
Definition
one carbon and two hydrogen atoms attached to the C atom bearing the -OH group. oxidized in two steps: to an aldehyde then to a carboxylic acid
Term
secondary alcohols
Definition
two carbon atoms and one hydrogen atom attached to the C atom bearing the -OH group. oxidation produces a ketone
Term
tertiary alcohols
Definition
have three carbon atoms attached to the C atom bearing the -OH . do not react with usual oxidizing agents
Term
aldehydes
Definition
any of a class or organic compounds characterized by the presence of a carbonyl group, in which the carbon atom is bonded to at least one H atom. pleasant odors. oxidation products of primary and secondary alcohols
Term
ketones
Definition
any of a class of organic compounds characterized by the presence of a carbonyl group, in which the carbon atom is bonded to two other carbon atoms. pleasant odors. oxidation products of primary and secondary alcohols
Term
carboxylic acid
Definition
any of a class of organic compounds characterized by the presence of a carboxyl group. reactions with bases gives carboxylate anions
Term
esterification reaction
Definition
carboxylic acids (RCO2H) reacts with alcohols (R'OH) to form esters (RCO2R'). the OR group of the alcohol ends up as part of the ester
Term
hydrolysis
Definition
reaction that is the reverse of the formation of the ester, generally done in the presence of a base, producing the alcohol and a sodium salt of the carboxylic acid
Term
amides
Definition
form when an acid reacts with an amine, with a loss of water. have an organic group and an amino group attached to the carbonyl group
Term
polymers
Definition
giant molecules made by chemically joining many small molecules called monomers
Term
thermoplastics
Definition
soften and flow when heated and harden when cooled
Term
thermosetting plastics
Definition
initially soft but set to a solid when heated and cannot be resoftened
Term
addition polymers
Definition
made by directly adding monomer units together (ex PVC)
Term
condensation polymers
Definition
made by combining monomer units and splitting out a small molecule (often water)
Term
elastomers
Definition
synthetic organic polymers with very high elasticity
Term
copolymers
Definition
formed by polymerization of two or more different monomers
Term
condensation reaction
Definition
two molecules react by splitting out, or eliminating, a small molecule
Term
polyester
Definition
condensation polymer formed by elimination of water b/w two types of monomers, one with two carboxylic acid groups and the other w/two alcohol groups
Term
polyamide
Definition
condensation polymer formed by elimination of water b/w two types of monomers, one with two carboxlic acid groups and the other with two amine groups
Term
Boyle's law
Definition
the volume of a fixed amount of gas at a given temperature is inversely proportional to the pressure exerted by the gas. PV=P'V'
Term
Charles's Law
Definition
the volume of a fixed quantity of gas at constant pressure decreases with decreasing temperature. V/T=V'/T'
Term
Avagadro's hypothesis
Definition
equal volumes of gases under the same conditions of temperature and pressure have equal numbers of particles (PV=nRT)
Term
Dalton's law of partial pressures
Definition
the pressure of a mixture of ideal gases is the sum of the partial pressures of the different gases in the mixture
Term
mole fraction, X
Definition
number of moles of a particular substance in a mixture divided by the total number of moles of all substances present
Term
diffusion
Definition
mixing of molecules of two or more gases due to their random molecular motions
Term
effusion
Definition
movement of gas through a tiny opening in a container into another container wher the pressure is very low
Term
ion-dipole forces
Definition
forces of attraction b/w a positive or negative ion and polar molecules, depends on distance, charge on ion, and magnitude of dipole
Term
enthalpy of solvation/hydration
Definition
enthalpy change associated with the hydration of ions/in water (depends on 1/d)
Term
hydrogen bond
Definition
extreme form of dipole-dipole interaction where one atom involved is always H and the other is highly electronegative
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