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Org Mol > Alkenes and Cycloalkenes > Flashcards

Alkenes and Cycloalkenes Flashcards

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1
Q

react with hydrogen gas to increase the number of hydrogen atoms to become __

A

alkanes

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2
Q

contain double and triple bonds

A

alkenes
alkynes

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3
Q

do not contain the maximum number of hydrogen atoms

A

unsaturated hydrocarbons

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4
Q

contain carbon-carbon double bonds

A

alkenes

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5
Q

general formula of alkenes

A

CnH2(n-m)

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6
Q

shape of alkene molecules

A

flat or planar

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7
Q
  • formed after the connection of orbitals of the same atom.
  • result from combinations of orbitals within a given atom, either prior to or as bonding with another atom takes place
A

hybrid orbitals

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8
Q
  • formed when orbitals of two different atoms merge
  • result from combinations or orbitals between atoms as bonding takes place to form molecules
A

molecular orbitals

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9
Q

concept of mixing atomic orbitals to form new hybrid orbitals suitable for the pairing of electrons to form chemical bonds in valence bond theory

A

orbital hybridization

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10
Q
  • single bond
  • results from an end-to-end orbital overlap
  • strongest type of covalent chemical bond
A

sigma bond

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11
Q
  • results from multiple bonds
  • forms from side-to-side orbital overlap
A

pi bond

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12
Q

when a carbon is connected to three other things, the molecule is modeled by combining the __ and __ to produce ___

A
  • 2s
  • two 2p
  • three sp2 orbitals
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13
Q

all three sp2 orbitals are at the same __ __

A

energy level

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14
Q

the sp2 orbitals are arranged in a __ __ __ around the central carbon atom

A

trigonal planar shape

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15
Q

angle of sp2 orbital bond

A

120 degrees

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16
Q

the unhybrid p orbital is __ to the plane

A

perpendicular

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17
Q

because of pi-bond, __ __ is not possible around carbon-carbon bonds

A

free rotation

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18
Q

in longer alkyl chains, the additional carbon atoms are attached to each other by __ __ __

A

single covalent bonds

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19
Q

alkenes also form __

A

stereoisomers

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20
Q

why do alkenes also form stereoisomers

A

rotation around multiple bond is restricted

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21
Q

isomers that have two similar atoms lying on the same side of the double bond in a molecule

A

cis isomer

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22
Q

isomers have molecules with two similar atoms that are placed on opposite sides of the double bond

A

trans isomer

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23
Q

alkenes having the substituents with higher priority on the opposite sides of the double bond

A

E isomers

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24
Q

alkenes having the substituents with higher priority on the same side of the double bond

A

Z isomers

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25
arrangement of cis position
Z
26
Z arrangement is from the word
zusammen = together
27
arrangements of trans position
E
28
E arrangement is from the word
entgegen = opposite
29
numbering of carbon atoms in alkenes
- start with the end nearest to the double bond - if the double bond is equidistant, begin at the end nearer the first branch point
30
numbering of carbon atoms in cycloalkenes
- double bond is between C1 and C2 - first substituent has a low number as possible - in molecules with more than one double bond, assign one double bond the numbers 1 and 2, and the other double the lowest number possible
31
alkenes substituents
alkenyl groups
32
most frequently encountered alkenyl groups
1. methylidene 2. ethenyl 3. 2-propenyl
33
common name: methylidene
methylene
34
common name: ethenyl
vinyl
35
common name: 2-propenyl
allyl
36
physical state of alkene
- colorless - odorless
37
ethene is an exepction at being odorless because it has a __ __ odor
faintly sweet
38
what are the alkenes that are gaseous in nature
first three (3) members
39
what are the alkenes that are liquid in nature
4-17 members
40
what are the alkenes that are solids in nature
18 above members
41
solubility of alkenes in water
insoluble in water due to nonpolar characteristics
42
where are alkenes soluble
nonpolar solvents such as benzene and ligroin
43
where does the melting point of alkenes depend upon
positioning of the molecules
44
isomer that have a lower melting point
cis-isomer
45
isomer that have a higher melting point
trans-isomer
46
polarity of alkenes
weak
47
alkenes are slightly __ __ than alkanes due to the presence of __ __
- more reactive - double bonds
48
- make up the double bonds - can easily be removed or added as they are weakly held
Pi (π) electrons
49
- produced naturally by all plants from the amino acid methionine and is a plant growth regulator - simplest alkene
ethene
50
where is ethene produced from
amino acid methionine
51
ethene causes trees to...
- lose their leaves - stems to thicken
52
Naturally occuring alkenes
1. ethene 2. pheromone 3. terpenes
53
compound used by insects (and some animals) to transmit a message to other members of the same species
pheromone
54
organic compound whose carbon skeleton is composed of two or more 5-carbon isoprene structural untis
terpenes
55
terpenes are composed of...
two or more 5-carbon isoprene structural units
56
other example of alkenes
1. propylene 2. b-carotene 3. a-pinene
57
produced as a by-product of petroleum refining and of ethylene production by steam cracking of hydrocarbon feedstocks
propylene
58
propylene is a by-product of...
- petroleum refining - ethylene production by steam cracking of hydrocarbon feedstocks
59
- orange pigment that gives carrots their color - important dietary source of vitamin A and is thought to offer some protection against certain types of cancer
b-carotene
60
- organic compound of the terpene class - found in oils of many species of many coniferous trees, notably the pine
a-Pinene
61
a-Pinene is found of many species of many __ trees, notably the __
coniferous pine
62
alkenes are generally perpared through __ __, in which two atoms on adjacent carbon atoms are removed, resulting in the formation of double bond
beta elimination
63
Methods in preparation of alkenes
1. Dehydration of alcohols 2. Dehydrohalogenation of alkyl halides 3. Dehalogenation of alkanes
64
molecule of water is eliminated from an alcohol molecule by heating the alcohol in the presence of a strong mineral acid
dehydration reaction
65
where does the double bond form in dehydration reaction
between adjacent carbon atoms that lost the hydrogen ion and hydroxide group
66
Dehydration reaction steps
1. Protonation of alcohol 2. Dissociation of the oxonium ion 3. Deprotonation of the carbocation
67
this step is a simple acid-base reaction, which results in the formation of an oxonium ion, a positively charged oxygen atom
protonation of the alcohol
68
this step produces a carbocation, which is a positively charged carbon atom and an unstable intermediate
dissociation of the oxonium ion
69
positively charged oxygen atom
oxonium ion
70
positively charged carbon atom
carbocation
71
- step where the positively charged end carbon of the carboncation attracts the electrons in the overlap region that bond it to the adjacent alpha carbon - electron movement makes the a carbon slightly positive
deprotonation of the carbocation
72
results in the deprotonation of the carbocation
hydrogen on alpha carbon becoming very slightlly acidic
73
- involves the loss of a hydrogen and a halide from an alkyl halide (RX) - normally accomplished by reacting the alkyl halide with a strong base, such as sodium ethoxide
dehydrohalogenation of alkyl halides
74
alkane molecules that contain two halogen atoms on adjacent carbon atoms
vicinal dihalides
75
vicinal dihalides can form alkenes upon reaction with __
zinc
76
Why are alkenes more reactive than alkanes
1. Weak bond 2. Electron density
77
hydrogen adds to the carbon of the double bond having the greater number of hydrogens
Markovnikov's rule
78
reaction in which one direction of bond forming or bond breaking occurs in the preferences to all other directions
Regioselective reaction
79
have double bonded carbon atoms bearing the same ligands
symmetrical alkenes
80
double bonded carbon atoms bearing different ligands
unsymmetrical alkenes
81
Aka cis and trans isomers
Geometric isomerism

Org Mol (12 decks)

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