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Org Mol > Alkenes and Cycloalkenes > Flashcards

Alkenes and Cycloalkenes Flashcards

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
Q

arrangement of cis position

A

Z

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26
Q

Z arrangement is from the word

A

zusammen = together

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27
Q

arrangements of trans position

A

E

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28
Q

E arrangement is from the word

A

entgegen = opposite

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29
Q

numbering of carbon atoms in alkenes

A
  • start with the end nearest to the double bond
  • if the double bond is equidistant, begin at the end nearer the first branch point
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30
Q

numbering of carbon atoms in cycloalkenes

A
  • 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
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31
Q

alkenes substituents

A

alkenyl groups

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32
Q

most frequently encountered alkenyl groups

A
  1. methylidene
  2. ethenyl
  3. 2-propenyl
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33
Q

common name:
methylidene

34
Q

common name:
ethenyl

35
Q

common name:
2-propenyl

36
Q

physical state of alkene

A
  • colorless
  • odorless
37
Q

ethene is an exepction at being odorless because it has a __ __ odor

A

faintly sweet

38
Q

what are the alkenes that are gaseous in nature

A

first three (3) members

39
Q

what are the alkenes that are liquid in nature

A

4-17 members

40
Q

what are the alkenes that are solids in nature

A

18 above members

41
Q

solubility of alkenes in water

A

insoluble in water due to nonpolar characteristics

42
Q

where are alkenes soluble

A

nonpolar solvents such as benzene and ligroin

43
Q

where does the melting point of alkenes depend upon

A

positioning of the molecules

44
Q

isomer that have a lower melting point

A

cis-isomer

45
Q

isomer that have a higher melting point

A

trans-isomer

46
Q

polarity of alkenes

47
Q

alkenes are slightly __ __ than alkanes due to the presence of __ __

A
  • more reactive
  • double bonds
48
Q
  • make up the double bonds
  • can easily be removed or added as they are weakly held
A

Pi (π) electrons

49
Q
  • produced naturally by all plants from the amino acid methionine and is a plant growth regulator
  • simplest alkene
50
Q

where is ethene produced from

A

amino acid methionine

51
Q

ethene causes trees to…

A
  • lose their leaves
  • stems to thicken
52
Q

Naturally occuring alkenes

A
  1. ethene
  2. pheromone
  3. terpenes
53
Q

compound used by insects (and some animals) to transmit a message to other members of the same species

54
Q

organic compound whose carbon skeleton is composed of two or more 5-carbon isoprene structural untis

55
Q

terpenes are composed of…

A

two or more 5-carbon isoprene structural units

56
Q

other example of alkenes

A
  1. propylene
  2. b-carotene
  3. a-pinene
57
Q

produced as a by-product of petroleum refining and of ethylene production by steam cracking of hydrocarbon feedstocks

58
Q

propylene is a by-product of…

A
  • petroleum refining
  • ethylene production
    by steam cracking of hydrocarbon feedstocks
59
Q
  • 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
A

b-carotene

60
Q
  • organic compound of the terpene class
  • found in oils of many species of many coniferous trees, notably the pine
61
Q

a-Pinene is found of many species of many __ trees, notably the __

A

coniferous
pine

62
Q

alkenes are generally perpared through __ __, in which two atoms on adjacent carbon atoms are removed, resulting in the formation of double bond

A

beta elimination

63
Q

Methods in preparation of alkenes

A
  1. Dehydration of alcohols
  2. Dehydrohalogenation of alkyl halides
  3. Dehalogenation of alkanes
64
Q

molecule of water is eliminated from an alcohol molecule by heating the alcohol in the presence of a strong mineral acid

A

dehydration reaction

65
Q

where does the double bond form in dehydration reaction

A

between adjacent carbon atoms that lost the hydrogen ion and hydroxide group

66
Q

Dehydration reaction steps

A
  1. Protonation of alcohol
  2. Dissociation of the oxonium ion
  3. Deprotonation of the carbocation
67
Q

this step is a simple acid-base reaction, which results in the formation of an oxonium ion, a positively charged oxygen atom

A

protonation of the alcohol

68
Q

this step produces a carbocation, which is a positively charged carbon atom and an unstable intermediate

A

dissociation of the oxonium ion

69
Q

positively charged oxygen atom

A

oxonium ion

70
Q

positively charged carbon atom

A

carbocation

71
Q
  • 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
A

deprotonation of the carbocation

72
Q

results in the deprotonation of the carbocation

A

hydrogen on alpha carbon becoming very slightlly acidic

73
Q
  • 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
A

dehydrohalogenation of alkyl halides

74
Q

alkane molecules that contain two halogen atoms on adjacent carbon atoms

A

vicinal dihalides

75
Q

vicinal dihalides can form alkenes upon reaction with __

76
Q

Why are alkenes more reactive than alkanes

A
  1. Weak bond
  2. Electron density
77
Q

hydrogen adds to the carbon of the double bond having the greater number of hydrogens

A

Markovnikov’s rule

78
Q

reaction in which one direction of bond forming or bond breaking occurs in the preferences to all other directions

A

Regioselective reaction

79
Q

have double bonded carbon atoms bearing the same ligands

A

symmetrical alkenes

80
Q

double bonded carbon atoms bearing different ligands

A

unsymmetrical alkenes

81
Q

Aka cis and trans isomers

A

Geometric isomerism

Org Mol (12 decks)

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