Chapter 2 Flashcards
conformations: different … of atoms that result from … about a single bond
spatial arrangements; rotation
staggered conformation: atoms/ groups on adjacent carbons are as
far apart as possible
eclipsed conformation: atoms/groups on adjacent carbons are as
close as possible
compounds reside in … conformational state
lowest E
eclipsed conformation is less stable because of
hyperconjugation
in staggered conformation, highest molecular orbital overlaps with
smallest antibonding molecular orbitals
… conformation: all conformations between staggered and eclipsed
skew
anti conformation is when the groups are … apart
180 degrees
gauche: groups are
60 degrees apart
torsional strain: resistance to …, non-bonded atoms separated by 3 bonds forced from … to …
rotation; staggered; eclipsed
angle strain: bond angle is …/… compared to optimum values
expanded; compressed
steric strain: non-bonded atoms separated by 4+ bonds are
forced closer to each other
strain: a measure of the energy stored in a compound due to a
structural distortion
dihedral angle: the angle created by two …, each defined by … atoms
intersecting planes; three
the energy difference between the conformational extremes arise from the stabilization of the staggered conformation. This arises because of a small … interactinon between a filled C-H bonding MO of one carbon and the empty/unfilled C-H antibonding MO on the adjacent carbon with which it is aligned
donor-acceptor
puckering of the ring alters the strain energy in two ways:
(1) it decreases the … associated with eclipsed interactions but
(2) it increases further the … caused by the compression of C–C–C bond angles
torsional strain; angle strain
a boat conformation is considerably less stable than a chair because of th e… associated with four pairs of eclipsed C-H interactions and the … between the two “flagpole” hydrogens
torsional strain; steric strain
some of the strain in the boat conformation can be relieved by a slight twisting of the ring to a … conformation
twist-boat
as the size of the alkyl substituent increases, the preference for conformations with the group … increases
equatorial
alkanes are … hydrocarbons, containing only C-C …
saturated; single bonds
alkanes are … hydrocarbons because the physical properties of the higher members of this class resemble those of the long C-chain molecules we find in … and …
aliphatic; animal fats; plant oils
a hydrocarbon that contains one or more C-C double bonds, triple bonds, or benzene rings, is classified as an … hydrocarbon
unsaturated
alkane names (based on number of C): C: C2: C3: C4: C5: C6: C7: C8: C9: C10: C11: C12: C13: C14: C15: C16: C17: C18: C19: C20:
methane; ethane; propane; butane; pentane; hexane; heptane; octane; nonane; decane; undecane; dodecane; tridecane; tetradecane; pentadecane; hexadecane; heptadecane; octadecane; nonadecane; eicosane
alkanes have the general molecular formula
CnH2n+2
constitutional isomers are compounds that have the same … but different …
molecular formula; structural formulas
by “different structural formulas” we mean that constitutional isomers differ in the kinds of … they have (.., ..,. or …) and/or in the … of their atoms
bonds; single; double; triple; connectivity
to determine whether two or more structural formulas represent constitutional isomers, write the … of each and then compare them. all compounds that have the same molecular formula but different … are constitutional isomers
molecular formula; connectivities
The IUPAC name of an alkane with an unbranched chain of carbon atoms consists of two parts: (1) a … that indicates the number of .. atoms in the chain and (2) the … -ane to show that the compound is a …
prefix; carbon; suffix; saturated hydrocarbon
The IUPAC name of an alkane with a branched chain consists of a … that indicates the longest chain of C atoms in the compound and … names that indicate the groups bonded to the parent chain
parent name; substitutent
a substituent group derived from an alkane by the removal of a hydrogen atom is called an …; it is commonly represented by the symbol …
alkyl group; R–
We name alkyl groups by dropping the -ane from the name of the parent alkane and adding the suffix …
-yl
(Rules of IUPAC system) the name for an alkane with an unbranched chain of C atoms consists of a prefix showing the number of … in the chain and the ending ..
C atoms; -ane
(Rules of IUPAC system) for branched-chain alkanes, select the longest chain of C atoms as the … chain; its name becomes the root name
parent
(Rules of IUPAC system) Give each substituent on the parent chain a name and a number. the number shows the … of the … to which the substituent is bonded. use a hyphen to connect the number to the name
carbon atom; parent chain
(Rules of IUPAC system) if there is one substituent, number the parent chain from the end that gives the substituent the
lower number
(Rules of IUPAC system) if there are two or more identical substituents, number the parent chain from the end that gives the lower number to the substituent … The number of times the substituent occurs is indicated by a … A … is used to separate position numbers
encountered first; prefix (e.g. di, tri); comma