Which Pair of Molecules Both Contain Carbon Atoms

Which Pair of Molecules Both Contain Carbon Atoms.

Alkenes

Alkenes
are hydrocarbons which contain carbon-carbon double bonds.  Their full general formula is CnH2n
for molecules with 1 double bond (and no rings).  Alkenes are as well known equally
olefins, after the original proper noun for ethene,
olefiant gas.

Alkenes accept office in a wide variety of chemical reactions, and are found as parts of many highly colored systems (run across beneath for examples).

Straight-concatenation and branched alkenes are named past using the stem that indicates the number of carbon atoms to which is added the suffix
-ene.  A locator number is placed immediately in front of the prefix to indicate which carbon number the double bail starts on.  Thus, the word “1-butene” indicates a chain of iv carbons, with a double bond between carbons one and two; the word “ii-butene” indicates a chain of four carbons, with a double bond between carbons 2 and 3.

Double-bonded carbons are
sp
2-hybridized, and have
trigonal planar
shapes, with the bonded atoms at angles of 120� to each other.
Free rotation is
not
possible around carbon-carbon double bonds in alkenes, making the carbon bondage less flexible and “floppy” than those of alkanes with the aforementioned number of carbons.  This lack of costless rotation too gives rise to
geometric isomerism
in alkenes (run into two-butene below for an example).

Alkenes are
nonpolar, since they comprise nothing but carbon-carbon and carbon-hydrogen bonds, and are not soluble in water; they are also generally less dense than water.

Many alkenes are isolated from petroleum, and may serve equally the starting points for the synthesis of more than complex molecules.


Ethene (Ethylene)

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Ethene
is more than commonly known under the lilliputian name
ethylene.  It is the simplest of the alkenes, consisting of ii carbon atoms connected past a double bond.  This leaves each carbon free to bond to two hydrogen atoms.  Since both carbon atoms are trigonal planar in shape, all six atoms prevarication in the same airplane, and ethylene is a flat molecule.  Information technology is a colorless gas (bp -103.ixC), having a sweet odor and taste.  Information technology is synthesized during the smashing of hydrocarbons at high temperatures, and can also exist produced from the dehydration of ethanol.  Information technology is used in the manufacture of the plastic polyethylene
(see section on Addition Polymers).  The release of ethylene stimulates the start of the ripening process in many plants; some fruits and vegetables are picked while unripe, when they are less fragile, and ripened when they reach their destination past exposure to ethylene gas.


Propene (Propylene)

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Propene, more commonly known as
propylene, is a colorless gas (bp -47.7C) produced in the cracking of hydrocarbons.  It is used in the manufacture of the polymer polypropylene.


ane-Butene

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i-Butene
consists of a chain of iv carbons, having a double bail between carbons 1 and 2.  Because carbon 1 has two of the same substituent (in this case, H), ane-butene does non exhibit geometric isomerism, different its structural isomer,
2-butene
(see below).


2-Butene

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two-Butene
is a structural isomer of 1-butene, having the double bail located between carbons 2 and 3.  Because gratuitous rotation is not possible around carbon-carbon double bonds, in that location are two isomers of two-butene:  ane in which the two methyl groups at the end are pointing to the aforementioned side of the molecule, known equally

cis-two-butene
:


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and one in which the 2 methyl groups are pointing to opposite sides of the molecule, known as

trans-2-butene
:


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Molecules which exhibit this kind of isomerism are known as
geometric isomers
(or
cis-trans isomers).  Despite the close similarity between these two structures, they are distinctly dissimilar compounds:  the
cis
isomer boils at iii.sevenC and melts at -139C, while the trans isomer boils at 0.88C and melts at -105.8C.


Chloroethene (Vinyl chloride)

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Chloroethene, or
vinyl chloride, is a carcinogenic gas manufactured from ethylene.  It is used in the manufacture of the plastic polyvinyl chloride (PVC).  The —CH=CH2
group occurs in many organic molecules, and is ordinarily known as the
vinyl group
(or more than formally as the
ethenyl group).



Tetrachloroethylene (Perchloroethylene, “Perc”)


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Tetrachloroethylene, amend known as

perchloroethylene
(“Perc”), and more officially as

tetrachloroethene
, is a non-flammable organic solvent, widely used in dry cleaning; it is besides used as an industrial solvent, degreaser, and paint remover.



2-Methyl-1-propene; Isobutylene


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Isobutylene
is copolymerized with isoprene to form
butyl rubber
(see entry on polyisoprene).


Muscalure

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Muscalure, or cis-nine-tricosene, is the sex activity pheromone of the female common housefly (Musca domestica).



1,3-Butadiene


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Molecules which accept two carbon-carbon double bonds are named with the suffix
-diene; hence a iv carbon chain with double bonds starting at carbon numbers 1 and 3 is named as
1,3-butadiene.  Molecules with carbon-carbon double bonds side by side to each other are referred to as
conjugated alkenes; molecules with large numbers of conjugated double bonds are responsible for many of the colors that we run across in the earth around us (see the section on Terpenes for examples).



i,2-Propadiene


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i,2-Propadiene
is an example of an
allene, in which at that place are 2 double bonds to the same carbon atom.  (In fact, the mutual name of i,2-propadiene is
allene.)  An interesting feature in the shape of these molecules is that the interior “double-double-bonded” carbon is
sp-hybridized, and the two pi-systems of the double bonds are perpendicular to each other; therefore the substituents on the outside double bonded carbon atoms are at correct angles to each other.



Cyclopropene


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Cyclopropene
is an instance of a
cycloalkene, a cyclic structure containing a carbon-carbon double bail.  In cycloalkenes smaller than cyclohexene, the double bond tin can just exist in the
cis-configuration, since the ring strain would exist likewise swell to adapt a
trans

double bond.  Cyclopropene itself is a highly strained molecule, since the bail angles are 60, which is very far from the ideal
sp
2-hybridized geometry of 120.


Cyclobutene

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Cyclobutene
is another highly strained molecule, with bond angles of approximately xc, which is once more very far from the ideal 120� geometry of alkenes.


Cyclopentene

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Cyclopentene
is not every bit highly strained as cyclobutene, since the bond angles of 108� are a little closer to the ideal 120� geometry of alkenes.



Cyclohexene


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Cyclohexene
rings are considerably less strained than the smaller cycloalkenes, and occur commonly in nature.



Cyclooctene


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cis-cyclooctene


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Cyclooctene
has a big enough ring that information technology can exist in both the
cis
and
trans
stereoisomers.
trans-Cyclooctene is a chiral compound, and tin can be found in ii enantiomeric forms:

trans-cyclooctene


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Cyclobutadiene


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Rings of 4 or more carbons can adapt 2 double bonds;
one,three-cyclobutadiene
is one case of this phenomenon.  Since the ring is as well pocket-size to suit two double bonds to the same carbon atom, the position numbers of 1 and 3 are frequently dropped from the name, since there is no other prepare of position numbers possible for the ring.



Cyclopentadiene


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1,3-Cyclopentadiene
is a band of five carbons containing ii double bonds.  As with cyclobutadiene, the position numbers can be dropped from the name, since no other positioning of the double bonds is possible.  When left to itself, cyclopentadiene undergoes a Diels-Alder reaction with itself, producing a dimer called

dicyclopentadiene
; this is the form in which cyclopentadiene is commonly sold.

Past heating the dicyclopentadiene is a distillation appliance, it is possible to “crack” the dimer back into the cyclopentadiene monomer, which distills out and tin can be collected in a cooled receiving flask.  Cyclopentadiene is a common reagent in organic labs for utilise as a reagent in diverse Diels-Alder reactions.



Cyclooctatetraene


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one,three,5,7-Cyclooctatetraene
was commencement synthesized by Richard Willst�tter in 1905.  Unlike benzene, it is not an aromatic chemical compound, despite having an alternate series of double and single bonds.  (See the section on Annulenes on the Aromatic Rings page.)

Terpenes, Terpenoids, and Essential Oils

The
terpenes
are a diverse grouping of natural products which tin can be considered as beingness composed of isoprene units (although their biosynthesis does non actually involve the isoprene molecule).  The
monoterpenes
incorporate ten carbon atoms, the
sesquiterpenes
have xv, the
diterpenes
have 20, the
triterpenes
have 30, the
tetraterpenes
have 40, and so on.  A number of related molecules too comprise oxygen, and are classified every bit
terpenoids.

Terpenes and terpenoids are found in many plants, and often have distinctive flavors and aromas.  They are oftentimes components of

essential oils
, and so named because they have a characteristic “essence” or fragrance. Many of these molecules are components of common foods and perfumes.  They can often be obtained from natural sources by steam distillation, or other fairly simple purification techniques.  Many of these compounds have important pharmaceutical and industrial uses, and may also be used as the starting betoken for the synthesis of other of import compounds.

Monoterpenes


Myrcene

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Myrcene
is establish in bay leaves and oil of bay.


Geraniol

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Geraniol
is constitute in roses (with 2-phenylethanol), citronella oil, pomerosa oil, geraniums, and other flowers.


Citral (Geranial)

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Citral, or
geranial, is institute in oil of lemon; it is also secreted by some insects to repel predators.  It is used commercially in lemon-smelling perfumes and in the synthesis of Vitamin A.  The structure shown here is citral-a; at that place is as well a citral-b isomer, in which the aldehyde and methyl group on the bottom double bond are in a
trans
relationship.


a
-Pinene

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a-Pinene
is the major component of oil of turpentine, which is obtained by steam distillation of the resin from several species of pine.


b
-Pinene

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b-Pinene
is constitute in oil of turpentine, but in much smaller amounts than
a-pinene.


a
-Terpineol

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a-Terpineol

is found in pine oil and juniper; it is used as a perfume and bactericide in many household cleaners.


(R)-(+)-Limonene

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Limonene
is isolated from oil of lemon or orange; information technology is found in the zest of the fruit.


(R)-(-)-Carvone

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(R)-Carvone
is found in spearmint oil.


(Due south)-(+)-Carvone

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(S)-Carvone
is found in caraway seed oil and dillseed oil; this molecule is the enantiomer of
R-carvone to a higher place.  The difference in orientation around the chiral carbon atoms gives these molecules a slightly dissimilar overall shape, resulting in slightly different odors when they interact with the olfactory receptors in the nasal passages.


Thujene

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Thujene
is found in oil of thuja, sage, tansy, and wormwood.


Thujone

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Thujone
is establish in oil of thuja, sage, tansy, and wormwood.


a
-Phellandrene

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The (-) stereoisomer of

a-phellandrene

is constitute in eucalyptus oils; the (+) stereoisomer is found in bitter fennel oil, ginger-grass oil, and cinnamon oil.


b
-Phellandrene

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The (+) and (-) stereoisomers of

b-phellandrene

is institute in a variety of essential oils, including water-fennel oil, lemon oil, and some eucalyptus oils.


Menthol

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Menthol
is establish in peppermint and other mint oils.  It has a pleasant cooling taste, since it causes the “cold” receptors on the tongue to actuate at higher temperatures than normal (such as trunk temperature).  It is used in cough drops, shaving lotion, and mentholated tobacco.


Menthone

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Menthone
is the oxidized form of menthol, and has a similar taste and physiological issue.


Cineole (Eucalyptol)

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Cineole,
or
eucalyptol,
is found in eucalyptus oils.  It is the active component of medicinal eucalyptus oils.


Camphene

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Camphene
is institute in turpentine oil, rosemary, cypress oil, and oil of citronella.


Camphor

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Camphor
is obtained from the wood of the camphor tree (found in Prc and Japan).  It is used medicinally as a counter-irritant (a substance which produces a superficial inflammation to reduce deeper inflammation) and an anti-itching agent.  It produces a cooling sensation, because it stimulates cold receptors (see menthol).  Its strong odor inspires deep breathing, but in large doses can lead to respiratory collapse.

Sesquiterpenes

Diterpenes



Vitamin A (Retinol)


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Vitamin A
(also known as
retinol) is a fatty-soluble vitamin, which is produced by the breakdown of the carotenes (especially
b-carotene).  It is institute in liver, egg yolks, butter, and milk.  Information technology is a precursor to retinal (come across below), the primary dye involved in vertebrate vision.  It is also involved in cell growth and maintenance of healthy skin tissue, bones, and teeth.

Triterpenes


Squalene

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Squalene
is found in shark liver oil, and is besides a major component of the lipids on the surface of human skin.  Although it is not obvious from the way the structure above is drawn, squalene is a forerunner for the biosynthesis of cholesterol.  Through a complex series of enzymatically controlled reactions, squalene is converted into an intermediate called lanosterol, which undergoes a number of subsequent reactions to become cholesterol.

Tetraterpenes

In addition to essential oils, terpenes and terpenoids are as well establish in naturally occurring dyes.  Molecules which contain large numbers of carbon-carbon double bonds adjacent to each other (a
conjugated

double bond arrangement) absorb lite at lower frequencies than molecules with no double bonds or simply a few double bonds; some of these compounds blot calorie-free in the visible region of the electromagnetic spectrum, and produce colors which we tin can come across.  (Compare the structures of the molecules below with the ones in the section on the Chemistry of Vision.)


Lycopene

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Lycopene
is a cerise pigment found in tomatoes, watermelon, guava, papaya, pink grapefruit, apricots, and rosehips.  Unripe tomatoes are green in colour because of their chlorophyll, merely as they ripen, the chlorophyll breaks down, unmasking the red color of the lycopene.  Lycopene is a proficient antioxidant, and is more readily absorbed from cooked tomatoes and tomato paste, especially if the foods contain fat.  This molecule, and the ones below, are structurally like to that of carotene, and are referred to as
carotenoids.


Zeaxanthin

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Zeaxanthin
is a yellow pigment found in corn, egg yolk, orange juice, mangoes; also contributes to the yellowish color of brute fats. Information technology is also found in the macula region of the retina (macula lutea, “yellowish spot”), where it filters out some blue and UV light, acting like internal sunglasses; macular degeneration is the most mutual cause of incomprehension in the elderly.  Carotenoids containing hydroxyl groups are sometimes referred to as

xanthophylls
.


Astaxanthin

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Astaxanthin
is a pink paint found in salmon, trout, ruby seabream and the carapaces of lobster and shrimp. In live shellfish, the astaxanthin forms a circuitous with a poly peptide which gives it a blackish color; when the shellfish are boiled, the protein breaks down, unmasking the pink astaxanthin.


Canthaxanthin

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Canthaxanthin
is a pinkish paint found in the feathers of American flamingos. It is obtained from shrimp in their diet; flamingos in captivity plough into obviously white birds unless they are fed acceptable amounts of shrimp.

The Chemistry of Vision

“I tin see clearly now . . .”


Vitamin A (Retinol)

See entry above.


b
-Carotene

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b

and

a-Carotene

are tetraterpenes.
b-Carotene absorbs blue and indigo light, giving information technology an orange color; it is found in carrots, yams, mangoes, and persimmons. The yellow color of butter and animate being fats comes from carotene and related molecules. Carotene is found along with chlorophyll in photosynthetic organisms; it protects cells past reacting with O2
molecules. The yellow color of autumn leaves is due to the carotene, which is unmasked every bit the chlorophyll in the leaves breaks downwardly.
b-Carotene is broken down in the body into 2 molecules of Vitamin A.


a
-Carotene


a-Carotene

is different from
b-carotene in the position of the double bond on the far right.  It is broken downward in the body into 1 molecule of Vitamin A.


g
-Carotene

In

g-carotene
, the one of the cyclohexene rings in
b-carotene is opened up, changing the location of one double bond.  It is broken downward in the body into i molecule of Vitamin A.



Retinal and Vision

Retinal
is the oxidized form of Vitamin A, having an aldehyde group at the end instead of an alcohol.  It combines with the protein opsin to form
rhodopsin, the principal light-gathering pigment in vertebrate retinas.  In the rod and cone cells in the retina, the retinal in rhodopsin is establish “at rest” in the
cis
form. When it absorbs a photon (hnorthward) of light, i of the
p-bonds is cleaved, causing the molecule to rotate and lock into the
trans
class, which has a completely different shape. This starts a long chain of chemical processes which eventually results in a visual image in the brain. The
trans-retinal molecule is then twisted dorsum into the
cis
form by another enzyme. When you look directly at a very bright lite, the “afterimage” that you lot encounter in forepart of your eyes is the upshot of a large amount of
cis-retinal having been transformed into
trans-retinal all at in one case; the enzymes take a niggling fleck of time to go through and “reset” all of these molecules back into the
cis
form.

References

P. West. Atkins,
Molecules, 2nd ed.  Cambridge: Cambridge Academy Press, 2003, p. 73-74, 77-78, 149-155, 164-173.

Paula Yurkanis Bruice,
Organic Chemical science, fourth ed.  Upper Saddle River:  Prentice Hall, 2004, p. 111-115.

Marye Anne Play a trick on and James Thou. Whitesell,

Organic Chemistry
, 3rd ed.  Sudbury:  Jones and Bartlett Publishers, p. 49-51, 79.

Maitland Jones, Jr.,
Organic Chemical science.  New York:  W. West. Norton & Visitor, 1997, p. 115, 136-138.

Richard J. Lewis, Sr.,
Hawley’south Condensed Chemical Dictionary, 13th ed.  New York:  Van Nostrand Reinhold, 1997.

Yard. Marc Loudon,
Organic Chemistry, fourth ed.  New York:  Oxford University Press, 2002, p. 111.

Robert Thornton Morrison and Robert Neilson Boyd,
Organic Chemistry, 6th ed.  Englewood Cliffs:  Prentice Hall, 1992, p. 273-285.

Royston M. Roberts, John C. Gilbert, and Stephen F. Martin.
Experimental Organic Chemistry:  A Miniscale Approach.  Fort Worth:  Saunders College Publishing, 1994, p. 122, 184.

D. West. A. Sharp,
The Penguin Dictionary of Chemistry, 2nd ed.  London:  Penguin Books, 1990.

Graham Solomons and Craig Fryhle,
Organic Chemistry, 7th ed.  New York:  John Wiley & Sons, Inc., 2000, p. 52, 287, 934-937, 1152-1157.

L. G. Wade, Jr.,
Organic Chemistry, 5th ed.  Upper Saddle River:  Prentice Hall, 2003, p. 272, 276-278.

Martha Windholz (ed.),

The Merck Index,

tenth ed.

Rahway: Merck & Co., Inc., 1983.

Which Pair of Molecules Both Contain Carbon Atoms

Source: https://www.angelo.edu/faculty/kboudrea/molecule_gallery/02_alkenes/00_alkenes.htm