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Transcript of Organic Chemistry
An alkane is a saturated hydrocarbon Defined as an unsaturated hydrocarbon with a cyclic structure, a chemically stable pattern of bonding and a strong aroma.
The simplest aromatic hydrocarbon is benzene (C6H6).
Has three double bonds and three single bonds Unsaturated hydrocarbon: an organic compound in which is comprised of both carbon and hydrogen atoms; however, the carbon are connected by double or triple bonds.
Alkenes and alkynes are unsaturated hydrocarbons.
Alkenes contain a double bond, and alkynes contain a triple bond 1. Identify longest carbon chain.
2. Identify substituent groups
3. Number the carbons so that lowest possible number is given to substituent group
4. Indicate the number of identical substituents using prefixes (di-, tri-, etc.)
5. List all substituents in alphabetical order in final name. Seperate numbers by commas and words by hyphens. Nomenclature By Raymond Chung, Reva Kyrollos, Michelle Tran, and Dilan Somanader Alkenes and Alkynes Aromatic Hydrocarbons General Formula CnH2n+2 Straight Chain Alkane have a long sequence of carbon atoms along a straight line.
Cyclic alkane (or cycloalkane) is a chain of carbon atoms joined to form a closed loop or ring structure.
General formula: CnH2n "A group of atoms found in the molecule which affects its properties" Functional Groups (Branches) Some hydrocarbons contain one or more hydrocarbon branches attached to the main structure of the molecule
An alkyl group is a branch attached to the main structure of the molecule, acts as substituent group A substituent group
is an atom or group of atoms that replaces one of the hydrogen atoms bonded to the central carbon atom. First Five Alkanes and their Alkyl Groups 1 Carbon = Methane - Methyl
2 Carbons = Ethane - Ethyl
3 Carbons = Propane - Propyl
4 Carbons = Butane - Butyl
5 Carbons = Pentane - Pentyl (notice that the alkyl groups end with -yl) Hybridization and Molecular Structure Hydrocarbons containing 4 or more carbon atoms exhibit structural isomerism:
two compounds have the same molecular formula but a different structure. There are 2 alkanes with C4H10, butane and methylpropane.
Butane is straight-chain, while methylpropane has branched structure
Because of change in structural arrangement, they exhibit different physical properties (butane has higher boiling point than methylpropane) A functional group is a group of atoms within a molecule that affect the properties of the compounds Alkanes are sp3 hybridized as each carbon has 4 sigma bonds. Example 1: Naming an Alkane 2. There are two methyl
groups attached to
the same carbon 1. Longest carbon chain is butane 3. Carbons are numbered
from side closest
to substituents 4. There are two methyl groups,
so the prefix di-
will be given 5. The final name is 2,2-dimethylbutane. 1 2 3 4 - Carbon and hydrogen have similar electronegativities, bonds are evenly arranged
- Molecule is non-polar
- Non-polar nature indicates weak intermolecular Van der Waals forces
- Low melting and boiling points
- Length of carbon chain has effect on the physical properties of alkanes
- Longer the carbon chain, the more likely it is to become 'entangled'
More energy required to untangle them
- Alkanes with longer carbon chains have higher melting and boiling points
-Alkanes are unreactive, does not react with acids, bases or oxidizing agents
Makes alkanes valuable for lubricating and structural materials such as plastics Properties of Alkanes Reactions Alkanes undergo complete combustion in the presence of oxygen Uses Alkanes are primarily used as fuels due to their combustive nature, releasing a lot of energy Examples include: Diesel Tar Gasoline Kerosene Cooking Oil Jet Fuel Sample Molecular Model:
Propane General Formula Alkene: CnH2n
Alkyne: CnH2n-2 Functional Group Alkenes are sp2 hybridized as the double-bonded carbon has only 3 s bonds Nomenclature Example 2: Naming an Alkene Example 3: Naming an Alkyne Physical Properties Reactions Method of Preparation Uses Molecular Models: General Formula Functional Group Hybridization A benzene ring is sp2 hybridized as the molecule is planar and all carbon atoms are bonded to three other atoms. Nomenclature Physical Properties Reactions Method of Preparation Molecular Model:
Benzene Example 4: Naming an Aromatic Hydrocarbon using Naming Convention #1 Uses When a benzene ring has lost one hydrogen atom, it is called a phenyl group, and behaves a substituent group. Functional groups replace hydrogen atom attached to central carbon
-Alkenyl and Alkynyl
Alkenes and Alkynes are more reactive
- they have double and triple bonds
- These bonds are less stable than single bonds, so they are more likely to take part in reactions ethylene propyne Alkenes:
Typically found in plastics
Shampoo bottles, polyethylene plastic bags
Used to synthesize compounds such as:
ethanol found in renewable fuel and polyvinyl chloride in ceiling tiles Benzene has been limited due to its harmful nature, but can still be found in:
•Gasoline/Petroleum CnH2n-6 When a benzene ring has lost one hydrogen atom, it is called a phenyl group, and behaves a substituent group. An addition reaction is when one molecule adding to another to form a single molecule.
Result: a single bond instead of a double or triple bond is formed hydrogenation reaction: hydrogen atoms are added on both sides of a double or triple bond halogenation reaction: a halogen reacting with an alkene or alkyne to form an alkyl halide. hydration reaction: water reacting with an unsaturated hydrocarbon to form an alcohol hydrohalogenation reaction: a hydrogen halide reacting with an alkene or alkyne. 4 types of addition reactions can occur... Cracking: breakdown of larger and more complex organic molecules into simpler and lighter hydrocarbons. This is classified as an endothermic thermal decomposition reaction as heat is involved. Alkenes and alkynes are both non-polar Higher boiling and melting points when compared to alkanes More carbon atoms in their chain/ring exist as either liquids or gases at room temperature. Typically liquid at room temperature This is due to its non-polar nature as a result of a symmetrical structure
Generally insoluble in water Bonding within a benzene ring causes it to be quite stable
does not easily undergo addition reactions Though they are less reactive than alkenes, they are still more reactive than alkanes Catalytic reforming: a mixture of hydrocarbons is combined with hydrogen gas and is exposed to a platinum chloride catalyst Products are separated from mixture using a solvent
Benzene is isolated using distillation (separating the individual components based on their ability to vapourize in boiling water) Regarded as a parent molecule. It is represented by a hexagon with a circle inside all bond angles equal 120°. Hybridization and Molecular Structure stereoisomer: a molecule which shares the same chemical formula and basic chemical structure as another molecule, but differs in the arrangement of the atoms. cis isomer: in this case, the atoms (or groups of interest) are situated on the same side of the double bond. trans isomer: the atoms are situated on opposing sides of the double bond. Alkenes are sp2 hybridized as the double-bonded carbon has only 3 s bonds.
Alkynes are sp hybridized since a carbon atom containing a triple bond only has 2 s bonds. 2C4H10(g)+13O2(g) --> 8CO2(g)+10H2O(g)+ thermal energy Alkanes can also undergo substitution reactions, in which an alkane reacts with a halogen to form an alkyl halide and a hydrogen halide. CH4 + Cl2--> CH3Cl + HCl Greater electronegativity difference between halogen and carbon, so molecule will be polar. Therefore, melting and boiling points will be higher. 1) Does the length of a chain affect the boiling point? 2) What is the backbone of aromatic hydrocarbons called? 3) Cis isomers have groups located on the ____ side. Trans isomers have groups located on _____ sides. 4) What happens with alkanes in complete combustion with oxygen? 5) What are some uses of alkanes? Yes, the longer the chain, the higher the boiling point. Chemists take advantage of this fact to separate mixtures of alkanes (called fractional distillation) like crude oil from the ground. In addition, the temperature of mixture of hydrocarbon slowly increases. Benzene Same for cis, and opposite for trans There is a greater electronegativity difference between halogen and carbon, making it polar. The melting and boiling point will be high as well. Diesel, tar, kerosene, gas, cooking oil and jet fuel. It produces carbon dioxide, water and thermal energy. Questions Thank You! 1. Identify the longest carbon chain/ring
2. Determine whether the molecule contains a double or triple bond (double is an alkene and a suffix of -ene, triple is an alkyne and a suffix of -yne)
3. If there is more than one multiple bond, indicate using a suffix (i.e. -diene, -triene)
4. Number the carbon chain so that the multiple bond is given the lowest number
5. Name and number the substituents using the same rules as for alkanes
*If the multiple bond is found in the middle of the chain, begin numbering from the side closest to a substituent group 1. The longest carbon chain is pentane 2. This molecule contains double bonds, so it is an alkene 3. There are two double bonds at the first and third carbons, so the suffix -diene will be given 4. Carbon chain is numbered 1. 2. 3. 4. 5. Therefore, the name of this alkene is penta-1,3-diene 1. The longest carbon chain is heptane 2. This molecule contains a triple bond, so it is an alkyne 3. There is only one triple bond, so no suffix is needed 4. Carbon chain is numbered. The triple bond is on the 3rd carbon. *Indicate the location of the multiple bond in the name of the parent chain. 5. There is an ethyl group on the fifth carbon. The name of this molecule will be 5-ethylhept-3-yne 1 2 3 4 5 6 7 1 2 3 4 5 6 1. The substituents are attached to the benzene ring, so the root name is -benzene. 2. Number the carbon ring so that the two closest substituents get the lowest number. 3. There are three methyl groups present on the 1st, 2nd, and 4th carbons The name of this molecule is
1,2,4-trimethylbenzene Example #5: Naming an Aromatic Hydrocarbon using Naming Convention #2 1 2 3 4 5 6 1. The longest carbon chain is hexane 2. Number the
carbon chain. 3. There is a phenyl group attached
to the third carbon This molecule is called 3-phenylhexane Two naming conventions Naming Convention #1: Benzene as the parent molecule
The root name will be -benzene
For a single group attached to the benzene ring, the name of the group attached is written before the root.
For two or more groups attached, the carbon atoms are numbered beginning from the first substituent
The numbering then continues in the direction of the next closest substituent. Naming Convention #2: Benzene as a substituent group In this case, the substituent will be referred to in the name of the compound as “phenyl”. Alkynes:
Found commonly as fuel in welding torches (oxyacetylene) 19th century Russian chemist Vladimir Markovnikov formulated Markovnikov's Rule, which is used to predict what product will form and how the atoms will be added to the double or triple bond. Markovnikov's Rule states:
“When a hydrogen halide or water molecule reacts with an alkene, the hydrogen atom will generally bond to the carbon atom in the multiple bond that has the most hydrogen atoms already bonded to it.” Hydrocarbons - Organic molecules consisting of hydrogen and carbon only. Classes of Hydrocarbons