A substituent on a __ can occupy either an __ or an __ position. In many cases, the reactivity of the substituent depends on whetehr its position is __ or __.
cyclohexane ring (in the chair conformation)
axial or an equatorial position
axial or equatorial
when two conformations are in equilibrium because they interconvert
The chair with a methyl group in an __ is the msot stable conformation, about 7.6 kJ/ mol lower in energy than the conformation with the methyl group on the __.
However, both of these chair conformations are lower in energy than any __.
The axial methylcyclohexane has two __, each representing about 3.8 kJ of additional eergy.
The __ has no __. Therefore, we predict that the __ is higher in energy by 7.6 kJ per mole.
equatorial methyl group
Explain a 1,3-diaxial interaction.
the involvement of substitents on carbon atoms of the ring that bear a 1,3 relationship
True or False:
1,3-diaxial interactions are present in equatorial conformation.
A larger group usually has a __ between the __ and __ becuase the __ is stronger for larger groups.
larger energy difference
axial equatorial positions
The __ between substituents in __ is particularly severe when there are __ on two carbon atoms that bear a __, as in the __ of __ shown in the text.
two chair conformations of cis 1,3-dimethylcyclohexane
The less stable conformation has __ in __.
both methyl groups
__ does not have a conformation with a __ between two __ groups. Either of its __ palces one __ in an __ and one in an __. These conformations have __, and they are present in equal amounts
The most stable conformation of the cis isomer of 1,3-dimethylcyclohexane has the methyl groups as what?
both methyl groups in equatorial positions
Either conformation fo the rans isomer of 1,3-dimethylcyclohexane places the methyl groups?
What does this mean?
one methyl group in an axial position
trans isomer is higher in ergery than the cis isomer by about 7.6 kJ/ mol, the energy differece between axial and equatorial methyl groups
True or Fals:
Cis and trans isomers cannot interconvert and there is no equilibrium between these isomers
In many substituted cyclohexans, the substituents are __.
The energy difference between the axial and equatorial positions for a larger group is __ than for a smaller gorup.
Ing eneral, if both groups cannot be __, the most stable conformation has the __ adn the __.
larger group equatorial
smaller group axial
Some groups, sucha s tertiary-butyl groups, are so bulky that they are extremely __ in __ positions. Regardless of the other gorups present, cyclohexanes with tert-butyl substituents are most stable when what?
the tert-butyl group is in an equatorial position
If two tert-butyl groups are attached to the ring, both of them are much less strained in__. When neither __ allows both bulky groups to be __, they may force the ring into a __.
twist boat conformation
Two or more rings can be joined into __ or __ systems. There are three ways that two rings may be joined: name them
most common, sharing two adjacent carbon atoms adn the bond between them
also common, sharing two nonadjacent carbon atoms (the bridgehead carbons) and one or more carbon atoms (the bridge) between them
in which two rings share only one carbon atom, are relatively rare
The name of a bicyclic compound is based on the name of the __
alkane having the sme number of carbons as there are int he ring system following the prefix bicyclo and a set of brackets enclosing three numbers
All fused and bdirdged bicyclic systems have __ connecting the __ where the rings connect.
two bridgehead atoms
The bumers in the brackets give what
the numer of carbon atoms in each of the three bridges conneting the bridgehead carbons, in order of decreasing size
__ is the most common example of a fused ring system.
The conformation of cis-decalin is somehwat __,but the trans-isomer is quite __. If one of the rings in the trans isomer did a __, the bonds to the second ring would both become __ and would be directed __ aprt. This is an impssible conformation and it prevents any __ in __.