Chapter 5 Flashcards
an unsaturated hydrocarbon contains one or more … or …
C-C double or triple bonds
the term unsaturation indicates that … are bonded to C than in an alkane
fewer hydrogens
alkenes contain a … and, with one double bond and no rings, have the general formula ..
C-C doulbe bond; CnH2n
A group derived by removal of an H from an arene is called an … group and is given the symbol …
aryl; Ar
when the aryl group substituent on a parent chain is a benzene ring, it is given the special name ..
phenyl group
the three double bonds in a six membered ring create a special stabilization called …, which lowers the reactivity of benzene relative to other alkenes
aromaticity
In other alkenes, deviations from the predicted angle of 120 degrees may be somewhat larger because of the … introduced by … created by groups bonded to the C of the double bond
strain; nonbonded interactions
the index of hydrogen deficiency is the sum of the number of … and … in a molecule
rings; pi bonds
index of hydrogen deficiency =
(Hreference - Hmolecule)/2
(index of H) replace each monovalent atom of halogens with … hydrogen; halogen substitutes for hydrogen and reduces the number of hydrogens by one per halogen.
one
(index of H) no correction is necessary for the addition of divalent atoms of … elements. They don’t change the number of hydrogens
group 6
(index of H) for each atom of a trivalent group 5 element, …
add one hydrogen
for the unhybridized 2p orbitals to be parallel, thus giving maximum overlap, the two Cs of the double bond an the four bonded atoms must
lie in a plane
rotation about a C-C double bond … under normal conditions
does not occur
whereas rotation about the C-C single bond is relatively free, rotation about the C-C double bond is
severely restricted
because of restricted rotation about a C-C double bond, any alkene in which each carbon of the double bond has two different groups bonded to it shows
cis, trans isomerism
cis alkenes with double bonds in open chains are .. than their trans isomers because of … between alkyl substituents on the same side of the double bond
less stable; steric strain
To form IUPAC names for alkenes, change the -an- infix of the parent alkane to
-en-
(IUPAC naming rules for alkenes)
1. number the longest carbon chain that contains the double bond in the direction that gives the … the lowest possible numbers
Cs of the double bond
(IUPAC naming rules for alkenes) 2. indicate the location of the double bond by the … of its first carbon
number
(IUPAC naming rules for alkenes) 3. name branched or substituted alkenes in a manner similar to alkanes
4. number the carbon atoms, locate and name …, locate the double bond, and name the …
substituent groups; main chain
methylene:
a … group
vinyl: a … group
allyl: a … group
CH2=; CH2=CH-H-; CH2=CHCH2-
CH2=CH2: …
CH3CH=CH2: …
CH3 CH3C=CH2: ...
ethylene; propylene; isobutylene
for more complex alkenes, the orientation of the atoms of the parent chain determines whether the alkene is
cis or trans
The E, Z system uses the priority rules of the … to assign priority to the substituents on each carbon of a …
R,S system; double bond
if the groups of higher priority are on the same side of the double bond, the configuration of the alkene is … If they are on opposite sides of the double bond, the alkene is …
Z; E
In naming cyclocalkenes, the carbon atoms of the ring double bond are numbered 1 and 2 in the direction that gives the substituent encountered first the … The 1 C, though, starts at the …
smaller number; double bond
To date, trans-cyclooctene is the smallest trans cycloalkene that has been prepared in … form and is … at room temperature. Trans cycloalkenes are not very …
pure; stable; stable
a bridgehead carbon is a carbon that is contained in both … of the hydrocarbon
rings
for alkenes containing two or more doulbe bonds, the infix -en- is changed to .., .., and so on. Those alkenes that contain several double bonds are also referred to more generally as …
-adien-; -atrien-; polyenes
For an alkene with n C-C double bonds, each of which can show cis, trans isomerism, … stereoisomers are possible
2^n
the only attractive forces between alkene molecules, which are nonpolar, are …
dispersion forces
alkenes are insoluble in water but soluble in …, in other … liquids, and in …
each other; nonpolar organic; ethanol
