Chapter 11 Organic Chemistry The study of the compounds of carbon

Some Properties Typical of Organic Compounds Organic compounds form covalent bonds have low melting points and boiling points tend to be flammable are soluble in non-polar solvents are not very soluble in water Oil and water A Review of the Bonding in Carbon Compounds of Carbon and Hydrogen Carbon has 4 valence electrons, and hydrogen has 1; to achieve an octet, C forms four bonds We will use a line __ to indicate the sharing of 2 electrons

You may recall that when 4 groups are attached to a central atom, the groups arrange themselves so they point to the corners of a tetrahedron The following illustrates 4 different but equivalent ways of illustrating the structure of methane: Compound solely of carbon and hydrogen are called hydrocarbons; if more than on carbon atom is present, then the molecule must have carbon-carbon bonds. The molecule shown below is called ethane CH3CH3 different ways of writing ethane

If carbon can form stable bonds to itself, there is no reason why there can’t be hydrocarbon composed of more than 2 carbons

Butane (butane lighter) has the following structures: Although the two forms of butane shown differ in the orientation of the CH3 groups circled, rotation of the groups as shown occurs quite rapidly Butane, C4H10 has one other feature worth describing. In the structure shown above, each carbon is either attached to one or two other carbon atoms. Consider a different way in which these four carbon atoms can be attached The lower molecule is called isobutane

If we consider hydrocarbons with 5 carbons, you can imagine a number of ways of putting the carbon backbone together CH3-CH2-CH2-CH2-CH3 C – C – C All of these compounds have a molecular formula of C5H12 are referred to as structural isomers. All are known compounds Structural isomers have similar but different properties and can be distinguished from one another by identifying carbon atoms that have different number of carbon atoms attached Are these structural isomers? These are two different ways of drawing the same compound

butane Some different ways of writing butane; all of then refer to the same compound because of rotation about the carbon-carbon bonds

A systematic way of naming alkanes and identifying identical structures 1. Locate the longest carbon chain in the molecule: this identifies the parent alkane the longest carbon chain is 4: butane 2. Identify the points of branching and count the number of carbons in each branch 2 points of branching at the same carbon: each 1 carbon 3. Name the branch on the basis of the number of carbons by dropping the ane of the parent and adding yl: methane methyl 4. Give the first branch encountered the lowest number and use the prefix di, tri, tetra, ... for multiple groups 2 methyl groups both at carbon 2 2,2-dimethylbutane

Name the following: hexane parent: groups position of groups both methyl 2 at carbons 2 and 4 2,4-dimethylhexane parent: groups position of groups heptane 2 chlorines and methyl chlorine at positions 3 and 5, methyl at position 3 Cl as a group is named chloro 3,5-dichloro-3 methylheptane

Name this compound: 5, pentane longest carbon chain groups: chloro, methyl CH3 at C2 and Cl at C3 location: 3-chloro-2-methylpentane CH3-CH2-CH2-CH2-CH2-CH2-CH-CH2-CH2-CH3 │ CH2CH3 longest carbon chain groups: 10, decane ethyl 4-ethyldecane location: ethyl at C4

What is a general molecular formula for these alkanes? if n = the number of carbon atoms, note that the number of hydrogens is? 2n+2 The general formula for all the compounds is given by CnH2n+2 How many C? How many H? 8 18 2*8+2 = 18

. Can we make an alkane with n C but less the 2n+2 hydrogens? H-CH2CH2CH2CH2-H . cycloalkanes can have less the (2n+2) H’s C3H6 C4H8 C5H10 C6H12

parent: cyclohexane groups: ethyl, chloro location: 1, 3  1-chloro-3-ethylcyclohexane 1-ethyl-3-chlorocylohexane The textbook often draws hydrocarbons without all of the hydrogen shown. This is an abbreviated way of drawing the molecule. Please remember that carbon always has 4 bonds to it and if all the bonds are not designated, you need to assume there are hydrogens at these positions parent: groups: cyclopentane isopropyl isopropylcyclopentane

Properties of n-alkanes The properties of alkanes include being nonpolar insoluble in water less dense than water flammable in air Alkanes with 1–4 carbon atoms are methane, ethane, propane, and butane all are gases at room temperature all are used as heating fuels Alkanes with 5–8 carbon atoms are liquids at room temperature all are very volatile all are found in gasoline Alkanes with 9–17 carbon atoms are liquids at room temperature all have higher boiling points all are found in kerosene, diesel, and jet fuels Alkanes with 18 or more carbon atoms are waxy solids at room temperature are used in waxy coatings of fruits and vegetables

The hydrocarbons in crude oil are often cracked to produce smaller hydrocarbons which are separated by their different boiling points All hydrocarbons can be burned in oxygen to produce carbon dioxide and water C8H18 + O2 = CO2 + H2O + Heat C8H18 + O2 = 8CO2 + 9H2O + Heat C8H18 + 25/2O2 = 8CO2 + 9H2O + Heat 2C8H18 + 25O2 = 16CO2 +18H2O + Heat

.. Compounds of carbon with other elements Oxygen oxygen has 6 valence electrons; needs to form 2 bonds .. O If a molecule contains a hydroxyl (–OH) group, it is called an alcohol. The the oxygen atom is bonded to two carbon atoms it is called an ether (–C–O–C–) . ethyl alcohol, ethanol hydroxyethane O In both these cases, the oxygen is single bonded to carbon

Compounds of carbon with other elements Nitrogen nitrogen has 5 valence electrons; needs to form 3 bonds .. N In an amine, nitrogen is attached by a single bond to 1, 2, or 3 different carbon atoms 2 carbons

A Summary of the typical functional groups encountered in organic chemistry are a characteristic feature of organic molecules that behave in a predictable way are composed of an atom or group of atoms are groups that replace a H in the corresponding alkane provide a way to classify families of organic compounds