Unsaturated Hydrocarbons

What is an unsaturated hydrocarbon?

It is a hydrocarbon in which one or more carbon-carbon multiple bonds (double bonds, triple bonds, or both) are present.

What is an addition reaction?

It is a reaction in which atoms or groups of atoms are added to each carbon atom of a carbon-carbon multiple bond in a hydrocarbon or hydrocarbon derivative. This behavior contrasts with that of alkanes, where the most common reaction type, aside from combustion, is substitution.

What is a unsymmetrical addition reaction?

It is an addition reaction in which different atoms (or groups of atoms) are added to the carbon atoms of a carbon-carbon multiple bond.

What are skeletal isomers?

Skeletal isomers are constitutional isomers that have different carbon-chain arrangements as well as different hydrogen atom arrangements.

Unsubstituted alkenes with more than 17 carbon atoms and one double bond are what at room temperature?

solids

What is a cycloalkene?

A cycloalkane is a cyclic unsaturated hydrocarbon that contains one or more carbon-carbon double bonds within the ring system.

What is a halogenation reaction?

A halogenation reaction is an addition reaction in which a halogen is incorporated into molecules of an organic compound. In alkene halogenation, a halogen atom is added to each carbon atom of a double bond, Chlorination (Cl₂) and bromination (Br₂) are the two halogenation processes most commonly encountered. No catalyst is needed.

What is a hydration reaction?

A hydration reaction is an addition reaction in which H₂O is incorporated into molecules of an organic compound. In alkene hydration, one carbon atom of a double bond receives a hydrogen atom and other carbon atom receives an -OH group. Alkene hydration requires a small amount of H₂SO₄ (sulfuric acid) as a catalyst.

What is a hydrogenation reaction?

A hydrogenation reaction is an addition reaction in which H₂ is incorporated into molecules of an organic compound. In alkene hydrogenation, a hydrogen atom is added to each carbon atom of a double bond. This is accomplished by heating the alkene and H₂ in the presence of a catalyst (usually Ni or Pt).

What is a hydrohalogenation reaction?

A hydrohalogenation reaction is an addition reaction in which a hydrogen halide (HCl, HBr, or HI) is incorporated into molecules of an organic compound. Require no catayst.

What is a pheromones?

A pheromone is a compound used by insects (and some animals) to transmit a message to other members of the same species. Pheromones are often alkenes or alkene derivatives.

What is an addition polymer?

A polymer in which the monomers simply "add together" with no other products formed besides the polymer. The simplest alkene addition polymer has ethylene (ethene) as the monomer. With appropriate catalysts, ethylene readily adds to itself to produce polyethylene.

A copolymer

A polymer in which two different monomers are present.

What is a terpenes?

A terpene is an organic compound whose carbon skeleton is composed of two or more 5-carbon isoprene structural units. Isoprene (2-methyl-1,3-butadiene) is a five-carbon diene.

What are alkene isomers?

Alkene isomers are compounds that have the same molecular formula (that is, the same numbers and kinds of atoms) but that differ in the way the atoms are arranged. Isomers, even though they have the same molecular formula, are always different compounds with different properties.

What is an alkene?

An alkene is an acyclic unsaturated hydrocarbon that contains one or more carbon-carbon double bonds. The alkene functional group is thus a C=C group.

What is a polymerization reaction?

Chemical reaction in which the repetitious combining of many small molecules (monomers) produces a very large molecule (the polymer).

What is an alkyne?

An alkyne is an acyclic unsaturated hydrocarbon that contains one or more carbon-carbon triple bonds. As the family name alkyne indicates, the characteristic "ending" associated with a triple bond is yne.

What are the combustion products are what?

As with any hydrocarbon, the combustion products are carbon dioxide and water.

Molecular formula for the methylene (methylidene) group

CH₂=

Molecular formula for vinyl (ethanol) group

CH₂=CH-

Molecular formula for allyl ( 2-propenyl) group

CH₂=CH-CH₂

Molecular formula for the simplest cycloalkene (cyclopropene)

C₃H₄

What is the common (non-IUPAC) name for the alkene ethene?

Ethylene

What is a symmetrical addition reaction ?

It is an addition reaction in which identical atoms (or groups of atoms) are added to each carbon of a carbon-carbon multiple bond. Two most common examples of symmetrical addition reactions are hydrogenation and halogenation.

What is a functional group?

It is the part of an organic molecule where most of its chemical reactions occur. Carbon-carbon multiple bonds are the functional group for an unsaturated hydrocarbon.

What is Markovnikov's rule?

Markovnikov's rule states that when an unsymmetrical molecule of the form HQ adds to an unsymmetrical alkene, the hydrogen atom from the HQ becomes attached to the unsaturated carbon atom that already has the most hydrogen atoms.

Do unsaturated hydrocarbons have chemical properties similar to those of saturated hydrocarbons?

No! Unsaturated hydrocarbons are chemically more reactive than their saturated counterparts. The increased reactivity of unsaturated hydrocarbons is related to the presence of the carbon-carbon multiple bond(s) in such compounds. These multiple bonds serve as locations where chemical reactions can occur.

What is an alkyl group?

Noncyclic hydrocarbon substituent in which a carbon-carbon double bond is present.

What are tow important types of naturally occurring substances to which alkenes contribute?

Pheromones and terpenes.

Define polymer and monomer.

Polymer is a large molecule formed by the repetitive bonding together of many smaller molecules. The smaller repeating unites of a polymer are called monomers.

What are positional isomers?

Positional isomers are constitutional isomers with the same carbon-chain arrangement but different hydrogen atom arrangements as the result of differing location of the functional group present. Positional isomerism is not possible for "alkanes" because they lack a functional group (e.g., double and triple carbon-carbon bond).

What is the common (non-IUPAC) name for the alkene propane?

Propylene

Do unsaturated hydrocarbons have physical properties similar to those of saturated hydrocarbons?

Yes!

Aside from combustion, nearly all other reactions of alkenes take place where?

carbon-carbon double bond

Alkenes with 2 to 4 carbon atoms are what at room temperature?

gases

What are two important types of unsymmetrical addition reactions?

hydrohalogenation and hydration

Cis-trans isomerism

is possible for some alkenes. Such isomerism results from the structural rigidity associated with carbon-carbon double bonds: Unlike the situation in alkanes, where free rotation about carbon-carbon single bonds is possible, no rotation about carbon-carbon double bonds can occur.

Unsubstituted alkenes with 5 to 17 carbon atoms and one double bond are what at room temperature?

liquids

What are the three classes of unsaturated hydrocarbons?

the alkenes, the alkanes, and the aromatic hydrocarbons (all covered in chapter 13).

The three most frequently encountered alkyl groups

the one-,two-, and three-carbon entities, which may be named using IUPAC nomenclature (methylidene, ethanol, and 2-propenyl) or common names (methylene, vinyl, and allyl)