Chapter 22 Organic chemistry

 chemical compounds consisting primarily of carbon carbon  original definition came from the misperception that these compounds were always related to life processes life

Structure of carbon  1s 2 2s 2 2p 2  4 valence electrons (2s 2 2p 2 )  Strong tendency to share electrons  Strong tendency to form covalent bonds

Molecular Architecture  4 covalent bonds  tetrahedron  tetrahedron

 Strong tendency to form covalent bonds w/ H, O, N, S, P, and halogens

Molecular Diversity  Also bond to other carbons to form chains, rings, plates, networks

Forms of carbon 1.Diamond  Hardest known material  High density (3.514 g/ cm 3 )  High mp (3550 deg. C)

2.Graphite  Soft  Conducts electricity  High mp (3570 deg. C)  Used as a lubricant, “lead” pencils

3.Coal  Black, rock-like  Burns readily

4.Coke  Made by heating coal  Used for making steel

5. Charcoal

Carbon Compounds  Over 4 million known cmpds., natural and synthetic  Almost limitless # of possible structures

Can form isomers  Compounds w/ same formula but different structures

Hydrocarbons  Compounds of hydrogen and carbon

1. Alkanes  Hydrocarbons in which all carbon atoms are connected by single bonds

 Saturated – Each carbon atom is connected by single bonds

e.g. 2-methylheptane

 Naming of alkanes (p. 582) meth, eth, prop, ………. + ane e.g. methane e.g. methane

 Alkyl groups

Sources and uses of alkanes  Most from petroleum & natural gas  e.g. natural gas is 90 % methane  gasoline: heptane, isooctane, ….

Substitution reaction

Alkenes  Double bond between carbons  e.g. ethene  Naming: use alkane name, drop –ane, add –ene  Unsaturated (one or more double bond)

 Addition reaction:

Alkadienes  2 double bonds  e.g. 1,3 butadiene

Polymers  Lg. molecule made of repeating subunits  e.g. polyethylene

Alkynes  Triple bond  e.g. ethyne  Common name: acetylene

Cycloalkanes  e.g. cyclopentane

Aromatic hydrocarbons  e.g. benzene

Exhibit resonance:

para-dichlorobenzene para-dichlorobenzene

Examples of hydrocarbons 1.Petroleum  fractional distillation

2.Rubber  vulcanization

Alcohols  Hydrocarbons with one or more hydroxyl (-OH) groups  e.g. 1-propanol  Drop the –e of propane and add -ol

Preparation of alcohols

Common alcohols  Methanol (wood alcohol)

 Ethanol (grain alcohol) often denatured = often denatured =

 Ethylene glycol

Halocarbons  Alkanes in which one or more halogens are substituted e.g. e.g. e.g. e.g. dichloromethane tetrachloromethane dichloromethane tetrachloromethane (carbon tetrachloride) (carbon tetrachloride)

 Dichloro-diphenyl-trichloroethane (DDT)

 Polytetrafluoroethylene (PTFE) or Teflon

Ethers  Two hydrocarbon groups are bonded to the same oxygen atom Dimethyl ether methyl ethyl ether

Aldehydes and Ketones  Substituted hydrocarbons with a carbonyl group

Aldehydes  The carbon of the carbonyl group is attached to at least one H

Aldehyde naming  Drop the –e from the alkane name anf add –al methanal ethanal methanal ethanal  ( common name formaldehyde)

Ketones  Both bonds of the carbonyl group attached to carbons

Ketone naming  Drop the –e of the alkane name and add –one propanone propanone (common name acetone) (common name acetone)

cinnamaldehyde

vanillin

piperine

Carboxylic Acids  Contain the carboxyl group

Carboxylic acid naming  Drop the –e and add –oic acid ethanoic acid ethanoic acid (common name: acetic acid) (common name: acetic acid)

Esters  General formula

Ester naming  Name of the R’ group first + name of acid represented before substitution of H with R’ group Drop –ic of acid name and add -ate Drop –ic of acid name and add -ate

Preparation of esters

saponification

Common esters

Interesting organic compounds 1.polystyrene

2. trinitrotoluene