Chem 12 Chapter 2 Unsaturated Hydrocarbons
Chemical reactions of alkenes: Symmetrical Addition Reactants Halogenation reaction
In alkene halogenation, a halogen atom is added to each carbon atoms of a double bond (addition of Halogen) - no catalyst required
Chemical reactions of alkenes: Symmetrical Addition Reactants Hydrogenation reaction-
In alkene hydrogenation, a hydrogen ato is added to each carbon atom of a double bond (addition of H2) - catalyst is usually Ni or Pt
Terpenes example
Isorpene (2-methyl-1,3-butadiene) is a five carbon diene show picture in slide
Copolymers examples
Saran wrap -- chloroethene ( vinyl chloride) and 1,1-dichloroethene Styrene-butadiene rubber --1,3 butadiene and styrene in a 3:1 ratio
Cyclopropene (C3H4) is the
simplest cyloalkane - a three membered carbon ring system with one double bond
Isomerism and alkynes
*Cis- trans isomerism is not possible* due to the linearity 180 angles about an alkynes triple bond *Constitutional isomers are possible* - relative to the carbon chain (skeletal isomers) and to the position of the triple bond (positional isomers)
Unsaturated Hydrocarbons : Functional groups is subdivided into 3 groups
- Alkenes - Alkynes -Aromatic hydrocarbons
Characteristics of Alkenes
-Acyclic( not circular ) unsaturated hydrocarbons aht contain one or more carbon-carbon double bonds - functional group - C=C group - Names end with ene versus and --ene signifies the presence of a double bond
Properties of Alkynes
-similar to those of alkenes and alkanes -insoluble in water but soluble in organic solvents - densities less than that of water -boiling points increase with molecular mass -low molecular-mass alkynes are gases at room temperature * the bigger they are the higher their boiling point
Unsaturated Hydrocarbons: Functional Group
-structural feature of an organic molecule that is directly invovled in most of its chemical reactions -carbon- carbon double/triple bonds are the functional groups in unsaturated hydrocarbons
Nomenature: Alkene IUPAC rules
1. replace the alkane suffix -ane with the suffix -ene 2. Select as the parent carbon chain the longest chain of carbon atoms that contains both carbon atoms of the double bond 3. Number the parent chain beginning at the end nearest to the double bond 4. Give the position of the double bond in the chain as a single #, which is the lower-numbered carbon atom participating in the double bond
Chemical Reactions of Alkenes: Symmetrical Addition Reactions there are two
2 idential- either an H or Halogens Hydrogenation reaction Halogenation reaction
Nonmenature :Alkene IUPAC rules continued
5. use the suffixes -diene, -triene, -tetrene, - and so on when more than one double bond is present in the molecule 6. A number is not needed to late the double bond in unsubstituted cycloalkenes with only one double bond because that bond is assumed to be between carbons 1 and 2 7. In sunstituted cycloalkanes with only one double bond, the double-bonded carbon atoms are numbered 1 and 2 in the direction (clockwise or counterclockwise) that gives the first-encountered substituent the lower number 8. In cycloalkanes with more than one double bond within the rind, assign one double the numbers 1 and 2 and the other double bonds the lowest numbers possible
Naturally occurring Alkenes: Pheromones
A compound secreted or excreted by insects(and some animals and plants) the triggers a response in other members of the same species
Chemical Reaction of Alkenes: Chemical properties
Alkenes are very flammable -combustin products are carbon dioxide and water - Alkene + O2 --> CO2 + H2O
Fused ring aromatic hydrocarbons
Aromatic hydrocarbons whose structures contain two or more rings fused together
Alkynes examples
C2H2 C3H4 -if I can see the same when flipped its not an isomer
Cis- trans isomerism in alkenes:
Cis- trans isomerism in alkenes results from the structural rigidly associated with C=C bonds - rotation about C=C or (c triple bonds) are not possible
Alkenes General Formula
CnH2n
Cycloalkenes general molecular formula
CnH2n-2 -remove thwo H's within the cycle to form a double bond
Characteristics of Cycloalkenes
Cyclic(circular) unsaturated hydrocarbons with one or more carbon-carbon bonds within the ring system Those with more than one double bond are relatively common
Nomenature: Alkene Common Names (Non-IUPAC names) common names are used mostly for compounds Two most common
Ethylene- (IUPAC name- ethene) - CH2 = CH2 Propylene (IUPAC name-Propene) -CH2= CH-CH3
Halogen list
F2, Cl2, Br2, I2
Nomenclature: Alkenes as substituents Most frequently encountered alkenyl groups
Mentylidene (one-carbon) -common name-Methylene Ethenyl (two-carbon) -common name- Vinyl 2-propenyl (three-carbon) -common name Aliyl
3 need to be aware of:
Naphthalene Anthracene Phenanthracene add picture from last slide
Natural occurring Alkenes: Terpenes
Organic compounds whose carbon skeleton comprises two or more 5 carbon isoprene structural units
Physical properties of Alkenes and Cycloalkenes
Physical properties are similar to those of alkanes melting point of an alkene is usually lower than that of an alkane with same number of carbon atoms alkenes with 2 to 4 carbon atoms are gases at room temperature unsubstituted alkenes with 5 to 17 carbon atoms are liquids alkene with more than 17 carbons atoms are solids
Polymerization of Alkenes: Addition polymers
Polymers cannot be accurately represented by an exact formula -length of carbon chains vary with each polymer molecule - the notation used is independent of carbon-chain length add picture from slide 30
Ethene Methane
a flat molecule with bond angles of 120 a tetrahedral with bond angles of 105 add slide picture
Unsaturated Hydrocarbons
a hydrocarbon with *one or more carbon-carbon multiple bonds*
Polymerization of Alkenes: Addition Polymers Polymers-
a large molecule former by the repetitive bonding together of many smaller molecules
Nomenclature: Alkenes as Substituents Alkenyl group:
a noncyclic hydrocarbon substituent in which a carbon double bond is present
Addition polymer
a polymer in which monomers simply "add together" with no other products formed besides the polymer -it is similar to the addition reactions described previously except that there is no reactant other than the alkene or sunstitued alkenes
Chemical Reaction of Alkenes: Chemical properties Addition reaction
a reactin in which atoms or group of atoms are added to each carbon atom of a carbon-carbon multiple bond in a hydrocarbon or hydrocarbon dericative
Preparation of Alkenes: Dehydration reaction
a reaction characterized by the loss of a hydrogen atom from each of two adjacent carbon atoms, forming a carbon-carbon double bond.
What is the difference between alkene skeletal isomers and positional isomers?
add picture
Two of the simplest alkenes are ethene and propene
add picture of the two
Many Pheromones have
alkene structures -arrangement of double bonds (cis or trans) influences the biological activity of alkene-type pheromones
Alkynes-
an acyclic ( noncircular) unsaturated hydrocarbon (one or more mulitple carbon-carbon bonds) that contains one or more carbon-carbon triple bonds
Unsaturated Hydro carbons physical properties Unsaturated Hydrocarbons chemical properties
are similar to those of saturated hydrocarbons are distinct, chemical more reactive than saturated hydrocarbons
which has a higher melting point of butane or butene?
butane
Reactivity of unsaturated Hydrocarbons is due to
carbon-carbon multiple bonds -unsaturated hydrocarbons are more reactive
Constiutional Isomerism in Alkenes: skeletal isomers
constitutional isomers that possess different carbon-atom arrangements and that contain identical functional groups if functional groups are present
Constitutional Isomerism in Alkenes: Positional Isomers-
constitutional isomers that possess the same carbon-atom arrangement and that have differing locations for functional groups present (linked together in a line) add picture like slide 15
Alkenes
contain one or more carbon-carbon double bonds C=C
Alkynes
contain one or more carbon-carbon triple bonds
Aromatic hydrocarbons
exhibit a special type of "delocalized" bonding involving a six members carbon ring.
Addition polymer example
formation of polyethylene
Properties of and sources for *Aromatic hydrocarbons*
insoluble in water soluble in non-polar solvents less dense than water benzene is a colorless, flammable liquid that burns with sooty petroleum is the primary source of aromatic hydrocarbons
Alkynes functional group:
is a C to C triple bond group names end with suffix -yne the general formula is CnH2n-2
Cis and trans isomers are
isomers that exist when each of the two carbons of the double bond has two different groups attached to it
Overall unsaturated hydrocarbons are
more reactive have same physical property as SH's similar naming as SH's chemical properties are distinct
Preparation of Alkenes:
more reactive than alkanes
Nomenclature: Naming Benzene derivatives
name of the substituent is used as a prefix to the name benzene numbers of non numerical prefixes are used in the presence of more than one substituent -ortho 1,2 disubstitution -meta 1,3 disubstitution -para 1,4 disubstitution ( 3 substituents)
Terpene are widely disturbuted in isopene is the backbone of
nature more than 22,000 terpenes are found in biological systems and they are responsible for the characteristic ordors of many trees and plant fragrances terpenes
Polymerization of Alkenes: Addition Copolymers Copolymers-
polymers in which two different monomers are present
Aromatic Hydrocarbons: Bonding in Hydrocarbons Benzene
possesses a six-membered carbon ring represented using one of the following structures -*every other line has a double bond* picture 1 Equivalent nature of C-C bonds is aptly described using an average of the two structure - an alternative that uses a single stucture is picture 2
Line- Angle structural formulas for Alkenes and Cycloakenes: Diene-
represents more than one double bond is added to the end of then name when there 2 double bonds with alkenes example penta*diene* add picture of slides 13and 14
Preparation of Alkenes: Alkenes are not easily formed from alkanes- Easier alkene-produceing methods exist-
special catalysts and temperature of 500c requirred Dehydration of alchol- loss of water add little yellow boxed drawling if have time
Nomenclature for alkynes
the rules for naming alkynes are identical to those used to name alkenes, except the ending -yne is used instead of -ene * the tripple bond needs to have the lowest #
Pheromones example
the sexual attractant of the female silkworm is a 16-carbon alkene derivative containing an -OH group
alkene Cis-isomer
the two groups are located not the same side of the double bond
alkene trans-isomer
the two groups are located on the opposite sides of the double bond
Constitutional Isomerism in Alkenes: Alkene vs alkane
there are more alkene isomers possible for a given number of carbon atoms them there are alkane isomers
Chemical reactions of *Aromatic hydrocarbons*
they do not readily undergo the addition reactions characteristic of other unsaturated hydrocarbons Benzene undergoes substitution reactions Important substitution reactions are Alkylation Halogenation
Chemical Reactions of Alkenes: Unsymmetrical Addition Reactions Maokovnikov's rules
when an unsymmetrical molecule of the form of Hq reacts with an unsymmetrical alkenes, the hydrogen atom from the HQ becomes attached to the unsaturated carbon atom that already has the most hydrogen atoms
Polymerization of Alkenes: Butadiene- Based addition polymers
when dienes are used as monomers in addition polymerization reactions, the resulting polymers contain double bonds - double bonds are still unsaturated They are more flexible than ethane-based saturated polymers