Organic Chemistry

Organic Chemistry – the study of compounds containing carbon Organic chemistry was thought to be the study of products made from organisms Chemists obtain organic compounds in two principal ways: isolation from nature synthesis in the laboratory.  Compounds made in the laboratory are identical in both chemical and physical properties to those in nature.

85% of all known compounds are organic compounds. Why Organic Chemistry? Organic compounds are found everywhere around us (foods, flavors, fragrances, medicines, toiletries, cosmetics, plastic, paints, our body, and etc.). 85% of all known compounds are organic compounds. Chemists have discovered or synthesized more than 10 million organic compounds.

Typical properties of organic compounds They contain carbon atom. They have covalent bonds. They have low boiling point and melting point. They are flammable (almost all burn). They are soluble in nonpolar compounds. They can be gas, liquid or solid. Can form large molecules.

It is important to know: •Carbon: normally forms 4 covalent bonds and has no unshared pairs of electrons. •Hydrogen: forms 1 covalent bond and no unshared pairs of electrons. •Nitrogen: normally forms 3 covalent bonds and has one unshared pair of electrons. •Oxygen: normally forms 2 covalent bonds and has two unshared pairs of electrons. •Halogen: normally forms 1 covalent bond and has three unshared pairs of electrons.

Hydrocarbons are the large family of organic compounds and they contain only carbon and hydrogen atoms. Hydrocarbons are divided into the two groups: 1. Saturated hydrocarbon: a hydrocarbon that contains only carbon-carbon single bonds (alkanes) 2. Unsaturated hydrocarbon: a hydrocarbon that contains one or more carbon-carbon double bonds, triple bonds, or benzene rings.

Alkanes Alkanes are saturated hydrocarbon (they have only carbon-carbon single bonds). The molecular formula of this group is CnH2n+2 (n is number of carbon atoms). Chemical properties of alkanes: in general, they have low reactivity.

Physical properties of alkanes They are nonpolar. They are insoluble in water. They have a lower density than water. They have low boiling point and melting point. They can be gas (with 1 to 4 carbon atoms), liquid (with 5 to 17 carbon atoms) or solid (with 18 or more carbon atoms).

 The boiling point and the melting point of alkanes increase by increasing the number of carbon atoms. The boiling point and the melting point of alkanes decrease by increasing the number of branches.

IUPAC Names Name # carbons Structural Formula Methane 1 CH4 Ethane 2 CH3CH3 Propane 3 CH3CH2CH3 Butane 4 CH3CH2CH2CH3 Pentane 5 CH3CH2CH2CH2CH3 The names of organic compounds are determined by the IUPAC rules (International Union of Pure and Applied Chemistry). The stem of the name states the number of carbon atoms in the carbon chain of the compounds. The suffix, in this case –ane, indicates the alkane family.

IUPAC NAMES Name # carbons Structural Formula Hexane 6 CH3CH2CH2CH2CH2CH3 Heptane 7 CH3CH2CH2CH2CH2CH2CH3 Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3 Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3 Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

Mnemonic for first four prefixes Monkeys Eat Peeled Bananas First four prefixes Meth- Eth- Prop- But-

Complete Structural Formulas Show the bonds between each of the atoms H H   H  C  H H C H H H CH4 , methane In methane, CH4 the four valence electrons of carbon are shared with the single electrons of four hydrogen (H) atoms. Each pair of electrons is a single bond, which can be drawn as a line. When a structure is drawn to show each bond, it is called a complete structural formula.

More Alkanes H H Condensed Structural Formulas H C C H CH3 CH3 H H Ethane H H H H C C C H CH3 CH2 CH3 H H H Propane The complete structural formula for ethane shows the single bonds between two carbon atoms and six H atoms. The complete structural formula of propane shows the 3-carbon chain with single bonds to the attached H atoms. To write a condensed structural formula, the H atoms are written as a group next to their respective C atoms.

Learning Check A. What is the condensed formula for H H H H H C C C C H B. What is its molecular formula? C. What is its name?

Naming the unbranched alkanes The IUPAC name consists of two parts: A prefix that shows the number of carbon atoms (meth-, eth-, prop-, but-, pent-, hex-, hept-, oct-, non- and dec-). 2. The suffix “-ane”. CH4 Methane C2H6 Ethane C3H8 Propane C4H10 Butane

Substituent group: they are the branches in the organic compounds. They are derived from an alkane by removal of a hydrogen atom. They are named by dropping the “-ane” from the name of the alkane and adding the suffix “-yl” (we call them alkyl group).   CH3- Methyl C2H5- Ethyl C3H7- Propyl Note: some substituents are made from other elements:   -F Fluoro -Cl Chloro

Naming branched alkanes Write the alkane name of the longest continuous chain of carbon atoms. Number carbon atoms starting from the end nearest substituent. Give the location and name of each substituent (alphabetical order) as a prefix to the name of the main chain.

Naming side chains Names are made up of: side chains, root 3 Names are made up of: side chains, root 2,3-dimethylpentane Root is the longest possible HC chain Must contain multiple bonds if present Add -yl to get name of side chain

Naming side chains 3-methylhexane 4-ethyl-2,3-dimethylheptane 5-ethyl-2,4,6-trimethyloctane

Alkyl branches Branches on carbon chains CH3 methyl CH3CH2 ethyl

Branched Alkanes CH3 CH3CHCH3 methyl groups CH3 CH3 CH3CHCH2CHCH3 In the structural formula of an alkane, the alkyl group is typically attached vertically above or below the carbon chain.

Naming Branched Alkanes CH3 methyl branch CH3CH2CH2CHCH2CH3 6 5 4 3 2 1 Count A branched-chain alkane is named by indicating the attached groups on the longest carbon chain. In this example, the longest carbon chain has 6 carbon atoms.

Naming Branched Alkanes CH3 methyl branch CH3CH2CH2CHCH2CH3 6 5 4 3 2 1 Count 3-Methylhexane on third C CH3 six carbon chain group The chain is numbered to give the side group or methyl group a location on carbon 3 in the chain.

Naming Summary 1. Count the C’s in the longest chain 2. Name each attached group 3 Count the longest carbon chain to give the first attached group the smallest number 4. Name and locate each group

Learning Check A. CH3 CH3 CH3CHCH2CHCH3 B. CH3 CH3 CH3CH2CHCH2CCH2CH3

Solution A. CH3 CH3 CH3CHCH2CHCH3 2,4-dimethylpentane B. CH3 CH3 CH3CH2CHCH2CCH2CH3 CH3 3,3,5-trimethylheptane

Learning Check Write a condensed structure for A. 3,4-dimethylheptane B. 2,2-dimethyloctane

Solution A. 3,4-dimethylheptane CH3 CH3CH2CHCHCH2CH2CH3 CH3 2,2-dimethyloctane CH3 CH3CCH2CH2CH2CH2CH2CH3

Isomers Same molecular formula Same number and types of atoms Different arrangement of atoms Structural isomers are compounds that have the same molecular formula with different arrangements of the atoms.

Isomers Isomers: compounds with the same molecular formula but a different connectivity of their atoms. Cycloalkane: a saturated hydrogen that contains carbon atoms bonded to form a ring. A hydrocarbon that contains carbon atoms joined to form a ring is called a cyclic hydrocarbon.

Examples of Isomers CH3 The formula C4H10 has two different structures CH3CH2CH2CH3 CH3CHCH3 Butane 2-methylpropane When a CH3 is used to form a branch, it makes a new isomer of C4H10.

Learning Check Write 3 isomers of C5H12 and name each.

Solution CH3 CH3CH2CH2CH2CH3 pentane CH3CHCH2CH3 2-methylbutane CH3CCH3 2,2-dimethylpropane

Alkene An unsaturated hydrocarbon that contains a carbon-carbon double bond. The molecular formula of this group is CnH2n (n is number of carbon atoms). They have less hydrogen atoms than alkanes. C2H4 CH2=CH4 C3H6 CH2=CH-CH3

Numbering carbons 1-pentene Q- draw pentene A- Where’s the bond? We number C atoms Thus, naming compounds with multiple bonds is more complex than previously indicated Always give double bond the lowest number Q - Name these C2H4 2-butene Ethene 3-nonyne

Naming side chains Be sure multiple bond is in your longest chain Rule 1: choose the correct ending ene

Naming side chains ethyl methyl methyl 2-ethyl-4,4-dimethyl 1-hexene

Naming side chains Name the structures below 3-ethyl-2-methylpentane 3-ethyl-1,5,5-trimethylcyclohexene

Alkynes An unsaturated hydrocarbon that contains a carbon-carbon triple bond. The molecular formula of this group is CnH2n-2 (n is number of carbon atoms). They have less hydrogen atoms than alkanes and alkenes.

Naming unbranched alkenes and alkynes Use the IUPAC names for alkanes. For alkenes, we replace the suffix “-ane” of alkanes by “-ene”. For alkynes, we replace the suffix “-ane” of alkanes by “-yne”.

Naming branched alkenes and alkynes Name the longest carbon chain with a double or triple bond. Number the carbon chain starting from the end nearest a double or triple bond. Give the location and name of each substituent (alphabetical order) as a prefix to the name.

Aromatic Compounds Aromatic compounds: contains one or more benzene rings.   Benzene: is an unsaturated compound and it has the molecular formula C6H6 (six carbon atoms and six hydrogen atoms). Benzene has a ring structure Benzene as a branch is named phenyl.

Naming aromatic compounds 1. When one substituent group is attached to benzene, we write the name of group in front of benzene.

Naming aromatic compounds 2. When two or more substituents are attached to benzene, the ring is numbered to the lower numbers to the side groups.

Naming: common vs. IUPAC Common names used in the 1800’s are still used for some compounds today: Acetone Formic acid Acetylene The International Union of Pure and Applied Chemistry (IUPAC) was established in 1900s Frequent revisions to nomenclature Systematic method allows an infinite number of compounds to be named given a few rules

Drawing structures: it’s all good 2-butene CH3CH=CHCH3

Functional groups alcohol alkene ester ketone carboxylic acid

carboxylic acid ester ether aldehyde amine nitrile

Alcohols OH CH3-CH2-CH2OH Propanol

Functional Groups aldehyde O CH3CH2CH2C butanal H O ketone CH3CH2CCH2CH3 O ketone 3-pentanone Diethyl ketone

Functional Groups CH3 carboxylic acid O CH3CHCH2C OH CH3 carboxylic acid 3-methylbutanoic acid CH3CH2C O OCH2CH3 ester ethylpropanoate diethyl ester

Functional Groups ether CH3CH2 -O-CH2CH3 Diethyl ether ethoxyethane

Polymerization Polymers are huge molecules made by combining small molecules called monomers Example: Compounds with double bonds add on to each other, end-to-end forming cross-linked chains CH2 =CH2 + CH2 =CH2  -CH2-CH2-CH2-CH2-