Chapter 2 Flashcards
Characteristics of Unsaturated Hydrocarbons
They contain carbon-carbon multiple bonds.
They are unsaturated because more hydrogen atoms can be added if the multiple bonds are removed.
Alkenes: contain one or more _____ bonds
Double
Alkynes: contain one or more ______ bonds.
Triple
Aromatics: Contain ____ _____ bonds….
Contain 3 double bonds alternating with three single bonds in a six-carbon ring (benzene ring).
Aromatics have 3 double bonds and 3 single bonds forming a 6-carbon ring called…
benzene ring
Benzene is an …
aromatic
Acetylene is an…
Alkyne
Ethylene is an…
Alkene
Alkenes with ONE double bond have a general formula of…
CnH2n
Same as cycloalkanes
How many structural isomers have the formula C4H8?
3
What causes the number of structural isomers to increase rapidly?
An increase in the number of carbons
Not only branching variations but also double bond position
Name the steps of Alkene Nomenclature
Step 1: Name the parent chain (contains C=C bond)
Step 2: Number longest chain so double bond gets lowest # possible
Step 3: Locate C=C bond wish lowest numbered carbon
Step 4: Locate and name attached groups
Step 5: Combine all the names
Naming alkenes with double bonds follows the same rules as alkanes, except…
It uses different -ene endings to represent the 3 # of double bonds
EX) 2 double bonds= diene
3 double bonds= triene
4 double bonds= tetraene
When naming alkenes, be sure to indicate the location off all the ____ bonds, including those with rings.
multiple
In C=C bonds, what is formed by the carbon atoms?
sp² hybrid orbital
with one electron left in a 2p orbital
In alkenes, one 2s and two 2p orbitals mix to form…
the sp² hybrid
two of the 2p orbitals mix with the single 2s orbital to produce three sp² hybrid orgitals in a process called
Hybridization
In hybridization, one 2p orbital is….
Not hybridized and remains unchanged
What geometry do most alkenes have?
trigonal planar (with C=C double bond)
Is geometric isomerism possible in alkenes? Why?
Yes, because there is no free rotation about the C=C bond.
Decribe cis- isomers in alkenes
isomers have two similar or identical groups on the same side of the double bond
Describe trans- isomers in alkenes
isomers have two similar or identical groups on opposite sides of the double bond
Cis- Trans isomerism is important to biological processes like…
VISION
How are cis and trans isomerism important to vision?
Light strikes the retina, a cis double bond in the compound retinal is coonverted into a trans double bond, adjusting the eye to different lights.
Physical properties of Alkenes
No electronegative elements, Nonpolar, weak intermolecular forces, Soluble in nonpolar solvents, insoluble in water, less dense than water, unpleasant odor (gasoline like)
In alkenes, how many Carbons are gasses, liquids, and solids
1-4 carbons are gasses
5-17 carbons are liquids
18 or more carbons are solids
Contrast alkanes and alkenes
- Alkanes have only single bonds (saturated hydrocarbo) and alkenes have one or more C=C double bonds.
- Alkanes have a lower melting point, Alkenes have a higher melting point
- alkenes have unpleasant odor, alkanes are odorless
Compare Alkanes and Alkenes
- Both are nonpolar
- Both are insoluble in water
- Both are less dense than water
What makes alkenes chemically reactive?
The double bond
In halogenation, what is added and what is produced
In halogenation, a DIATOMIC HALOGEN is added
Halogenation (addition) reactions produce HALOALKANES
What is another name for haloalkanes
alkylhalides
In Hydrogenation ______ is added.
Hydrogen
Hydrogenation (addition) reactions can occur in the presence of what catalysts
Pt, Pd, Ni
What an example of hydrogenation in food
Hydrogenate vegetable oil to increase shelf life
can also make low-melting point solids (margarine and shortening)
What happens in Hydrohalogenation?
In hydrohalogenation an acidic halogen compound is added to produce haloalkanes
What are the acidic hydrogen halides in hydrohalogenation?
HF, HCl, HBr, HI
What alkene addition reactions follow markovnikov’s rule?
all UNSYMMETRICAL alkene addition reactions
What does markovnikov’s rule state?
It states that when a molecule of H-X adds to an alkene, the H predominantly attaches to the Carbon already bonded to the hydrogens
(THE RICH GET RICHER)
What phrase is used to describe markovnikov’s rule?
“The rich get richer”
When using markovnikov’s rule, you must state both _____ and ______ products.
Major and minor
Describe Hydration
In hydration, water (H-OH) is added to form an alcohol.
Follows Markovnikov’s rule
Requires acid catalyst.
Define Addition Reaction Mechanism
(hydration of alkenes)
The complete step-by-step descriptioon of exactly which bonds break and which bonds form in what order
What happens to the acid catalyst in reaction mechanism
it gives up a H+ ion which is attracted to the electrons of the C-C double bond
What is a carbocation
The carbocation is when the second carbon is left with only three bonds, giving it a positive charge.
reaction mechanism:
-In hydration, the oxygen atom has….
-One pair of oxygen electrons forms a covalent bond with…
1) two unshared electron pairs
2) the positive carbocation
What is an addition polymer?
a polymer formed by the linking together of many alkene molecules through addition reactions
What is polymerization?
when hudreds or thousands of alkenes can be added to each other to form long chained alkanes
Why is it impossible to give an exact formula for a polymer
because of different sizes
common names are used instead
Define both polymers and monomers
Polymers: very large molecules made up of repeating units
Monomer: the starting material that becomes the repeating units of a polymer
everyday examples of polymers
plexiglas and teflon
What is a copolymer
an addition polymer formed by the reaction of two different monomers
common polymers are…
polyethylene, polypropylene, poly vinyl chloride (PVC), polytetrafluorethylene (Teflon), Plexiglas, polyvinyl acetate, polyacryloaitrile, polystyrene (Styrofoam)
Alkynes (with triple bond) have a general formula of…
CnH2n-2
Are there a lot of alkynes found in nature?
No, there are only a few carbon-carbon triple bonds found in nature
What is the simplest and most important alkyne
ethyne (aka acetylene)
What is the alkyne ethyne/acetylene commonly used for
fuel for torches and making plastics
H-C(triple bond)C-H
acetylene
Steps of alkyne nomenclature
1) Name parent chain that contains triple bond
2) number chain so triple bond gets lowest number
3) locate and name all attached groups
4) combine all names
In alkynes, one 2s and one 2p orbitals mix to form the…
sp hybrid
A carbon- carbon sigma bond forms by the…
overlap of one sp hybrid orbital of each carbon
Physical properties of alkynes
- no electronegative elements
- nonpolar/ weak intermolecular forces
- insoluble in water
- soluble in nonpolar solvents
- less dense
- Low melting and boiling point
Chemical properties of alkynes
- halogenation, hydrogenation, hydrohalogenation, hydration
- react by addition reaction with Br2, H2, HCl, H2O
- two steps: first addition turns the alkyne into an alkene, the second addition turns the alkene into an alkane
- require twice as many moles of addition reagent as alkenes in reactions that go on to completion
How were aromatics found
Organic chemists found that fragrant oils extracted from certain plants had similar chemical properties. These cpds were aromatics because of their aroma
aromatics have a _____ ring of one of its …
benzene
Structural relatives
What general formula do aromatics have
C6H6
What are aliphatic compounds
Compounds that do not contain the benzene structure (alkanes, alkenes, alkynes)
What german chemist suggested the double bonds alternate positions between carbon atoms to give two equivalent structures
Freidrich Kekule
Who was Freidrich Kekule
german chemist who suggested the double bonds alternate positions between carbon atoms to give two equivalent structures
What does delocalized mean?
Spread out
When a single hydrogen attached to the benzene ring is replaced, the compound can be named as a….
derivative of benzene
(in aromatics) When the benzene ring is part of a more complex hydrocarbon, the benzene ring is referred to as a…
Phenyl group
What is a phenyl group
when the benzene ring is part of a more complex hydrocarbon (in aromatics)
When two groups are attached to the benzene ring, there positions can be designated by the prefixes:
- ortho (o) meaning the groups are next to eachother
- meta (m) meaning the groups are seperated by on carbon
- para (p) meaning the groups are opposite of eachother
Physical properties of aromatic compounds
- no electronegative elements
- nonpolar/ weak IF
- Insoluble in water (hydrophobic)
- Soluble in nonpolar solvents
What does hydrophobic mean
Insoluble in water
Chemical properties of aromatic compounds
- aromatic rings are relatively stable chemically and often remain intact during reactions
- benzene does not react like alkenes and alkynes
- benzene does undergo subsitiution reactions, in which a ring hydrogen is replaced by some other groups (not important)
Polycyclic aromatic compounds contain…
two or more fused benzene rings
Describe polycyclic aromatic compounds
- benzene rings share common side
- simplest polycicylic aromatic is naphthalene (active ingredient in mothballs)
- often known to be carcinogeninc, so often in tobacco smoke
What is the simplest polycyclic aromatic
Naphthalene (active ingredient in mothballs)
What does carciogenic mean
Cancer causing
this is why polycyclic aromatics are often found in tobacco smoke
Aromatics are used in commerical materials, industry, and living things. List examples
Commercial materials: Drugs and dyes
Industry: solvents
Living things: Vitamins and aa
