organic chemistry





Chapter 23: Organic Chemistry
December26 1999
23.1 What is carbon Compounds?
 carbon compounds are far more numerous and varied than compounds formed from other elements
 there are millions of different carbon compounds
 most are combinations with hydrogen, oxygen, nitrogen, sulfur, phosphorous, and the hologens
 some general and physical properties of carbon atoms are :
 non electrolytes, or very weak electrolytes
 low melting points
 compounds made solely from carbon and hydrogen are generally non-polar and insoluble in water
23.2 Where do Carbon Compounds come from?

Coal
 composed chiefly of carbon of carbon atoms, incorporated appreciable amounts of oxygen, nitrogen and sulfur compounds into it’s structure

Destructive distillation
 in which coal is heated in the absence of air, liberated many carbon compounds
Coal tar was separated into 200 different carbon compounds
 In order to maintain living conditions, organisms must synthesize numerous carbon-based molecules such as protein, fats, sugars, cellulose, etc.

 Since all the sources of carbon compounds came from living organisms, chemistry of carbon was called organic chemistry.

23.3 So many organic compounds
Why So Many?
The bonding Behavior of Carbon:
 For electrons available for bonding, electrons can be shared in four covalent bonds
 Carbon atoms can be linked together to form chains of various lengths
 Different arrangements of the same atoms result in different substances, each with unique chemical and physical identities
23.4 Sorting Out Organic Compounds
Hydrocarbons:
 Carbon compounds containing only carbon and hydrogen atoms
 Organic compounds in which some or all of the hydrogen atoms have been replaced by other atoms are consider derivatives of hydrocarbons
Carbon backbone (skeleton)
 Longest chain in a hydrocarbon molecule (e.g.)
 Simple molecules are called straight –chain or unbranched hydrocarbons(eg)

 more complex hydrocarbons may be composed of several carbon chains that cross, these are called branched hydrocarbons (eg)
 hydrocarbons may contain all single bonds or combinations of single, double and triple bonds
 saturated molecules cannot incorporate additional molecules into their structure, and entirely made up of single carbon-carbon bonds
 hydrocarbons containing at least one double pr triple carbon- carbon bond are referred to as unsaturated
Saturated unsaturated

23.5 Alkanes

 Straight ( or branched) chain, saturated compound containing only single bonds, result from fractional distillation (table 23.1 pg. 676)
 Relatively low boiling points because of the low degree of intermolecular attraction due to hydrocarbons being generally non-polar
Methane gas (CH4):
 Simplest of all alkanes
 Produced during anaerobic decomposition of organic substances
 Major constituent of natural gas
Ethane (C2H6):
 Contains one carbon-carbon single bond and six carbon-hydrogen bonds
 Constituent of natural gas
Propane (C3H8):
 Differs from ethane by the presence of a unit made up of one carbon atom and two hydrogen atoms -CH2-
 Also found in natural gas
 Homologous series – series of compounds whose members by addition of -CH2-
I.e. The alkane series
General formula : Cn H2n + 2
Number of carbon atoms
23.6 Naming Hydrocarbons

 Current procedure for naming organic compounds is based on a set of rules formulated by the International Union Of Pure and Applied Chemistry(IUPAC)
 Unbalanced alkanes are the simplest to name. They use Greek prefixes for the number of Carbons: pent, hex, hept, or oct, followed by the family endings “ane” (eg) heptane
 For branched chains, the name of the smaller portion uses “yl” which replaces the “ane” ending.
 (The branch is known as analkyl group).
Eg methyl heptane
 structural isomers are compounds with the same chemical formula but different structures( arrangement)
Eg. 2 methyl heptane 3 methyl heptane
 short form to show the presence of two groups when there is more than one branch off of a carbon backbone

 2,4 dimethylheptane


23.7 Alkenes

Cracking- the process used to produce organic molecules containing double- bonded carbon atoms

Alkenes series- consists of straight- or branched-chained hydrocarbons containing, at least one double carbon – carbon bond
General formula: Cn H2n
Note: the name of each alkene is similar to the alkane having the same number of carbon atoms, however the ending of the name is changed from –ane to –ene
 since the location of the double bond will influence the chemical behavior of the alkene, its position needs to be identified.
Eg. 2 pentene
 Alkenes are more reactive than the corresponding alkanes
 Ethene, C2 H4 is the simplest alkene:
 Commonly known as ethylene
 Has a slightly sweet odor
 Produced by certain plants or chemically [reduced
 One of the most important organic compounds in the chemical industry
23.8 Alkynes

 Contain a triple carbon-carbon bond
 Reactive
 Little energy is required to break