Unit 8 – Organic Chemistry

Text – Ch. 1 and 2

Intro to Organic Chem

• Originally, Organic Chemistry was the chemistry of living things.

• Chemists were aware of a very large number of organic compounds (such as dyes, soaps, vinegars, sugars, perfumes, gums, and rubber, to mention a few) but were unable to explain how so many compounds could be made from only a few elements.

• Swedish chemist Jöns Jakob Berzelius (1779–1848) had just explained inorganic compounds as being formed by oppositely charged atoms.

Intro to Organic Chem

• However, this did not explain organic compounds such as C2H6, C2H4, C3H8, C4H10, and so on.

• It was common knowledge that Cl2 could be substituted for H in C2H6 to produce C2Cl6. This meant, however, that a negative Cl could be substituted for a positive H. This was not consistent with Berzelius’s idea of oppositely charged atoms attracting.

Intro to Organic Chem

• Up to this point, no organic compound had been synthesized from inorganic materials and, as a result, many scientists believed that organic compounds were formed only under the influence of a vital force.

• It was Friedrich Wöhler (1800–1882) who, in 1828, made a remarkable discovery at the University of Göttingham in Germany. He attempted to prepare ammonium cyanate by means of a double decomposition reaction in a solution of ammonium chloride and silver cyanate.

Intro to Organic Chem

• Both of these compounds were considered to be inorganic.

• Instead of producing ammonium cyanate, however, he obtained crystals of urea, an organic compound.

NH4Cl + AgCHO AgCl + CH4N2O Urea

Intro to Organic Chem

• Within a few years of this event, when acetic acid and several other organic compounds had been prepared from inorganic materials, the validity of the vital force was questioned.

• As time passed, more and more organic compounds were synthesized from inorganic materials.

• It became obvious that it was not necessary for all organic compounds to be associated with living organisms.

Therefore,

Organic Chemistry is associated with all

molecules that contain carbon

Chemistry of Carbon

• Carbon has four valence electrons

– Therefore, it can bond four times per carbon

– Single bonds, double bonds, triple bonds

Hydrocarbons

• Hydrocarbon– Made of hydrogen and carbon

• Two classes of hydrocarbons

– Chains – Aliphatic and Cyclic hydrocarbons– Rings – Aromatics

Hydrocarbons

• Alkanes

– Are saturated hydrocarbons– All bonds are single and filled with hydrogen– Names end in “ane”

– General formula is CnH2n+2

• Ex. Methane, Ethane, Propane

Hydrocarbons

• Alkenes

– Are unsaturated hydrocarbons– Some bonds are single and filled with hydrogen, while

others are double bonds– Names end in “ene”– Give the position of the bond by using the smallest

numbers possible– General formula is CnH2n

– More reactive than alkanes

• Ex. Ethene, Propene, Propadiene

Hydrocarbons

• Alkynes

– Are unsaturated hydrocarbons– Some bonds are single and filled with hydrogen, while

others are triple bonds– Names end in “yne”– Give the position of the bond by using the smallest

numbers possible– General formula is CnH2n-2

– More reactive than alkenes

• Ex. Ethyne, Propyne

Hydrocarbons

• Cyclic Hydrocarbons– Hydrocarbons arranged in a ring– Chain end loses one H, and forms a bond– Name has “cyclo” in it

• Ex. Cyclohexane, cyclohexene

Hydrocarbons

• Aromatics– Contain a benzene ring– Called aromatic as most have distinctive odours– If a functional group, it is called “phenyl” group

– Benzene• Carcinogen, liquid (low mp and bp), insoluable in water, used to

make derivatives, flammable

• Examples – trinitrotolulene, napthalene, vanillin, salicylic acid, 2-phenyl butane– When you change the functional groups, you change the

structure

Hydrocarbons – functional groups and isomers

• Isomers– Two molecules which have the same formula but a

different structure– Therefore they react differently

• For methane, ethane and propane, there are no isomers or branches

• But butane, has two isomers

• Examples

Hydrocarbons – functional groups and isomers

• Rules for Naming Isomers (branched hydrocarbons)– Find the longest chain of carbons– Count from the end of the chain closest to the branch

or branches– Name the longest branch(es) then the chain– If the structure contains a double or triple bond, it

takes priority and is named and numbered from the bond

– Goes in alphabetical order

– Examples

Hydrocarbons – functional groups and isomers

• Functional Groups– CH3- R methyl

– CH3- CH2- R ethyl

– CH3- CH2- CH2- R propyl

– OH- R hydroxyl (alcohol)

– R – O – R ether

– NH2 – R amyl (amine)

Hydrocarbons – functional groups and isomers

• Some special ways to name are to look at the functional groups and the point at which they are bonded

– n – normal (on the end)– iso – in the middle– s - secondary– t – tertiary

• Examples– Isopropyl alcohol, t – butyl alcohol, 2 – butanol or s -

butanol

Hydrocarbons – functional groups and isomers

• Functional Groups (Cont)Carboxyl group Aldehyde

Organic acids

Ketone Amide

Ester – made from the condensation reaction of an alcohol and an organic acid

Reactions of Alkanes, Alkenes and Alkynes

• Alkanes– Without energy, alkanes generally are inert

– When they are exposed to a spark, they form carbon dioxide and water.

2 C4H10(g) + 13 O2(g) 8 CO2(g) + 10 H2O(g)

Reactions of Alkanes, Alkenes and Alkynes

• Alkanes (continued)

– When exposed to steam and extreme temperatures, alkanes break to form an alkene and hydrogen gas

– This is called thermal cracking or dehydrogenation and takes temperatures of 1400oC

Reactions of Alkanes, Alkenes and Alkynes

• Alkanes (Cont)– Going from alkenes to alkanes (or

hydrogenation) does not take as much energy as dehydrogenation

– In presence of a catalyst and hydrogen, the alkene adds the hydrogen at the carbons surrounding the double bond

Reactions of Alkanes, Alkenes and Alkynes

• Halogenation (Text p. 24 – 26)– Alkanes that react with heat or uv light, will go

through a substitution reaction, where a alkyl halide will be produced

– This is called a substitution reaction– If the reaction proceeds, a di-substitution

reaction takes place

Reactions of Alkanes, Alkenes and Alkynes

• Halogenation (p. 24 – 26)– Alkenes and alkynes are unsaturated and

more reactive than alkanes– Since no hydrogen is lost, this reaction is

called an addition reaction, and occurs at room temperature

– Alkenes and alkynes will react with halogens, as well as hydrogen halides and water

Reactions of Alkanes, Alkenes and Alkynes

• Reactions – Markovnikov’s Rule (p. 26)– When a reactant consists of non-identical

atoms (such as a hydrogen halide), and is added to an alkene or alkyne, the hydrogen atom bonds to the side of the double bond that has more hydrogen atoms

More Organic Reactions

• Aromatic Reactions (p. 28 and 29)

– Not very reactive

– Even though aromatics are unsaturated, they undergo substitution reactions, to form substituted benzene’s

More Organic Reactions

• Alcohols– Contain a hydroxyl group, which is in the

place of a hydrogen group– Where the hydroxyl group is will determine the

name (as mentioned before)– Made from the hydration reaction of an alkene

and water– A condensation reaction of two alcohols will

make an ether

More Organic Reactions

• Carboxylic Acids (Organic Acids)– Weak acids that have a vinegar type smell, which can

be used in law inforcement– Contain a carboxyl group that replaces the hydrogen

on the terminal carbon– Take the name of the molecule with “oic” in the name– Made from the oxidation of alcohols to aldyhydes and

then to acids– Relatively soluable in water with high bp– Used to make Esters

More Organic Reactions

• Esters (Organic “Salts”) (p. 64 – 67)– Account for many smells we are accustomed to

– Made from the reaction of a carboxylic acid and alcohol, which produces water (Condensation reaction) and can be broken apart by hydrolysis reactions

– The name is the alcohol, dropping the “ol” and adding “yl” and the acid, dropping the “oic” and adding “oate”

– Really cool!!!

Polymers

• Post a WIKI!!!