Saturday, July 21, 2012

Chapter 10 chemistry note



·         Organic compounds always contain carbon (C), usually hydrogen (H), and may also have other non-metallic elements such as oxygen (O), sulfur (S), nitrogen (N) or chlorine (Cl).
·         It must have four bonds and they will always have an H3 at the end.
·         Many organic compounds burn vigorously in air. Typically, organic compounds are not soluble in water.
·         Inorganic compounds are ionic, which leads to high melting and boiling points. Inorganic compounds that are ionic or polar covalent are usually soluble in water.
·         Most organic substances so not burn in air.
·         Hydrocarbons are organic compounds that consist only of carbon and hydrogen. The simplest hydrocarbon is methane, CH4.
·         A molecule with four atoms bonded to a central atom has a tetrahedral shape.
·         More than 90% of the compounds in the world are organic compounds. The large number of carbon compounds is possible because the covalent bond between carbon atoms is very strong, allowing carbons to form long, stable chains.
·         The alkanes are a class of hydrocarbons in which they are connected by only single bonds. One of the most common uses is fuels.
·         Alkane prefixes:
1.       Methane     CH4        
2.       Ethane          C2H6       CH3-CH3
3.       Propane       C3H8
4.       Butane         C4H10
5.       Pentane       C5H12
6.       Hexane        C6H14
7.       Heptane      C7H16
8.       Octane         C8H18
9.       Nonane        C9H20
10.   Decane         C10H22
·         In a condensed structural formula, each carbon atom and its attached hydrogen atoms are written as a group. A subscript indicates the number of hydrogen atoms bonded to each carbon atom.
·         The bonds can rotate freely about connecting the carbon atoms.
·         Hydrocarbons can also form cyclic structures called cycloalkanes, which have two fewer hydrogen atoms than the corresponding alkanes.
·         Cyclo always has two compounds less, the H2 is connected on each side, it’s not a straight line. When it cyclizes, it loses 2H atoms.
·        
 

                  cyclopropane                         cyclobutane      cyclopentane       cyclohexane
·         When an alkane has four or more carbon atoms, the atoms can be arranged so that a side group called a branch or substituent is attached to a carbon. An alkane with at least one branch is called a branched alkane.
·         When two compounds have the same molecular formula but different arrangements of atoms, they are called isomers.
·         The carbon branch is named as an alkyl group, which is an alkane that is missing one hydrogen atom.
o   CH3 = Methyl
o   CH3-­- CH2  = Ethyl
o   CH3-- CH2--CH2 = Propyl
o   F--, Cl--, Br--, I--, Fluoro, chloro, bromo, iodo
 

o   CH3—CH—CH3 = Isopropyl

  
·         How to write the alkanes with substituents
1.       Write the name of the longest chain
2.       Number the carbon atoms starting from the end nearest a substituent (stay in that direction once you start numbering)
3.       Give the location and name of each substituent as a prefix to the alkane name
4.       If there are more than one substituent, call them di, tri, or tetra as appropriate
5.       No number is necessary for a compound with one or two carbon atoms and one substituent
·         To figure out if the chain is an isomer or the same molecule, count the carbons and hydrogens. If they’re the same, just rearranged, they’re isomers. If they’re the same but not rearranged, just flipped around, they’re the same molecule.
·         Many types of alkanes are the components of fuels that power our cars and oil that heats our homes.
·         Alkanes are nonpolar, which makes them insoluble in water. However, they are soluble in nonpolar solvents such as other alkanes.
·         The first four alkanes- methane, ethane, propane, and butane- are gases at room temperature and are widely used as heating fuels.
·         Alkanes having five to eight carbon atoms –pentane, hexane, heptanes, and octane- are liquids at room temperature and are highly volatile, which make them useful fuels such as gasoline.
·         Liquid alkanes with nine to seventeen carbon atoms have higher boiling points and are found in kerosene, diesel, and jet fuels.
·         An alkane undergoes combustion when it completely reacts with oxygen to produce carbon dioxide, water, and energy. Carbon-carbon single bonds are difficult to break, which makes alkanes the least reactive family of organic compounds. Alkanes burn readily in oxygen.
·         In organic compounds, carbon atoms are most likely to bond with hydrogen, oxygen, nitrogen, sulfur, and halogens.
·         Within this vast number of compounds, there are specific groups of atoms called functional groups that give compounds similar properties.
·         The alkenes contain one or more double bonds between carbon atoms.
·         Alkynes contain triple bonds.
·         Aromatic compounds contain benzene, a molecule that has a ring of six carbon atoms with one hydrogen atom attached to each carbon.
 
·         The characteristic functional group in alcohols is the hydroxyl (-OH) group bonded to a carbon atom.
·         In thiols, the functional group –SH is bonded to a carbon atom.
·         In ethers, the feature is an oxygen atom bonded to two carbon atoms.
·         Aldehydes and ketones contain a carbonyl group (C=O), which is a carbon with a double bond to oxygen.
·         In an aldehyde, the carbon atom of the carbonyl group is bonded to another carbon and one hydrogen atom. It’s always at the end.
·         In a ketone, the carbonyl group is bonded to two other carbon atoms.
·         In carboxylic acids, the functional group is the carboxyl group, which is a combination of the carbonyl and hydroxyl groups.
·         An ester is similar to carboxylic acid, except that the oxygen of the carboxyl group is attached to a carbon and not to hydrogen.
·         In amines, the central atom is a nitrogen atom. Amines are a derivative of ammonia, NH#, in which carbon atoms replace one, two, or three of the hydrogen atoms.
·         An amide, the hydroxyl group of a carboxylic acid is replaced by a nitrogen group.

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