3 -- Part 1: STRUCTURE AND STEREOCHEMISTRY OF ALKANES
Explain the trends in their physical properties by drawing and naming the isomers of alkanes.
Draw alkane conformations, compare their energies, and predict the most stable ones.
Explain ring strain by drawing and naming the isomers of cycloalkanes.
Predict the most stable cycloalkanes by drawing the conformations of them.
A colorized radar image of the surface of the largest moon in the solar system.
The dark areas of low reflectivity are thought to be lakes of methane and ethane, which rain down on the moon and flow in rivers along its surface.
3 hybridized carbon have no functional groups.
There are no double or triple bonds in alkanes.
Poor acids and bases are what they are.
Alkanes are less reactive than other classes of compounds that have functional groups.
The study of organic compounds begins with the structure of alkanes.
Most organic compounds are named using the parent alkane as the root of the name.
Table 3-1 shows how we classify hydrocarbons according to their bonding.
Alkanes only have single bonds.
Even though their structures are different, any isomers of these compounds have the same formula.
Each time a carbon atom is added, the formula increases by two hydrogen atoms.
The general formula is for the unbranched alkanes.
The number of methylene groups in the chain is what distinguishes these alkanes.
Both butane and propane are related to decane and hexane.
It applies to branched alkanes as well.
Alkanes have the same formula.
The isomers isobutane, isopentane, and neopentane follow the rule.
The alkanes contain 42 carbon atoms with extensive branching.
If all alkanes had straight-chain structures, their names would be simple.
We need a way of naming the different isomers of alkanes.
There are two isomers of formula C4H10
Common names can't describe the larger, more complicated molecule.
As the number of carbon atoms increases, the number of isomers increases as well.
We need a system that allows us to name complicated molecules without having to memorize hundreds of historical common names.
A group of chemists representing the countries of the world met in 1892 to come up with a system for naming compounds that would be easy to use, and that would be flexible enough to name even the most complicated organic compounds.
The standard method for naming organic compounds is the IUPAC rules.
The IUPAC rules for naming organic compounds are summarized in Appendix 5.
Many different families of com pounds are named by the IUPAC system.
The naming of alkanes will be considered in detail, and later these rules will be extended to other compounds as we encounter them.
The main chain of carbon atoms is numbered and given the locations of side chains.
The process is governed by four rules.
The base name of the compound is the first rule of nomenclature.
Use the name of the longest continuous chain of carbon atoms as the base name of the compound.
The chain on the right has more substituents attached to it than the chain on the left.
The base CH3 CH3 CH3 name is given to all the different chains of that length.
The locations of the substituents can be given by assigning a number to each carbon atom on the main chain.
The end of the chain nearest a substituent is the longest.
We start the numbering at the end of the branch that has the lowest number of substituted carbons.
The first branch at C3 is given by numbering from top to bottom, but the first branch at C2 is given by numbering from bottom to top.
Numbering from bottom to top is correct.
Give the location of each alkyl group by the number of the main-chain carbon atom to which it is attached.
The use of alkyl group terminology is shown in the following alkanes.
The most common alkyl groups have up to four carbon atoms.
They are different from other kinds of propyl and butyl groups.
Common names for the simple branched alkyl groups are.
The isopropyl and isobutyl groups are similar to isobutane.
The main chain of eight carbons is found in the base name of 4-isopropyloctane.
There must be a group on the fourth carbon.
Decane has a main chain of ten carbons.
The halogen atom is treated as a substituent and can be named haloalkanes.
There are alkyl groups in the names of alkanes and haloalkanes.
Figure 3-2 shows when two or more substituents are present.
You will see them listed in alphabetical order.
When there are more than two substituents, list them in alphabetical order.
To avoid having to name the group twice.
Even if it means repeating a number more than once, include a position number for each substituent.
We can use this rule to make names for complicated structures.
Give a name for the compound.
The longest carbon chain has eight carbon atoms.
Numbering from left to right gives the first branch on C2; numbering from right to left gives the second branch on C3.
There are two on C2, one on C3 and one on C6.
There is a group on C4.
Use this chain as the base name if you want to find the longest continuous chain of carbon atoms.
The longest chain starts with the end nearest a branch.
Give the location of each substituent by the number of the main-chain carbon atom to which it is attached.
When there are more than two substituents, list them in alphabetical order.
The number in the structure is important to make sure they match.
The names are incomplete or incorrect.
Draw the structure to draw all C7H16 alkanes, and name it correctly.
A systematic method chain identifies complex alkyl groups.
The base alkyl group is the longest alkyl chain.
The base alkyl group has numbered structures, beginning with the "head carbon" bond to the main chain.
The sub and if a name appears twice, you stituents on the base alkyl group are listed with appropriate numbers, and parentheses have either duplicated a structure or are used to set off the name of the complex alkyl group.
The examples named something wrong.
Give the more common names to the following groups.
The structures of the compounds have been drawn.
Alkanes are used in a wide range of products.
Natural gas, gasoline, kerosene, heating oil, lubricating oil, and paraffin "wax" are all composed primarily of alkanes.
Alkanes can be dissolved in weakly polar organic solvents.
Alkanes are good for metals because they keep water out of the metal.
Thekanes are listed in Table 3-2.
The density of alkanes is around 0.7 g/mL.
Because alkanes are less dense than water and insoluble in water, a mixture of alkanes and water quickly separates into two phases.
The boiling points and melting points of the unbranched alkanes are given in Table 3-2.
The boiling points increase in strength as the number of carbon atoms increases.
Increased intermolecular van der Waals attractions are caused by larger molecule surface areas.
Vaporization and boiling must be overcome by these increased attractions.
Each additional CH2 group increases the boiling point by about 30 degC up to about ten carbons, and by about 20 degC in higher alkanes.
The difference in boiling points is due to the fact that branched alkanes are more compact.
The melting points increase with increasing molecular weight like their oil.
The point graph of the Macondo well is not smooth, but it floats on top of the water.
The carbon atoms pack can be burned off.
Higher temperatures are needed to melt the oil booms.
odd numbers of carbon atoms do not pack as well, and they melt at lower temperatures, which is why alkanes with nonpolar fibers are used.
The sawtooth-shaped graph of melting points is smoothed by drawing separate lines.
The Alkane is boiling.
Some branched alkanes are compared with CH3.
There are melting points.
In order of increasing boiling point, list each set of compounds.
Alkanes are separated into fractions with similar boiling points.
The fractions are suited for different uses based on their physical properties.
At room temperature and atmospheric pressure, methane and ethane are gases.
Natural gas is used for heating and power generation.
Methane and ethane are difficult to liquefy, so they are usually handled as compressed gases.
Methane and ethane become liquids when they are cooled to very low temperatures.
Propane and butane are gases at room temperature and pressure, but they can be easily liquefied under modest pressure.
Both propane and butane can be used for heating.
They burn cleanly and don't need pollution-control equipment.
In agricultural areas, propane and butane are more cost-effective than diesel and gasoline.
freons have mostly been replaced by propane and butane in aerosol cans.
The chlorofluorocarbons are implicated in damaging the ozone layer.
The volatile liquids are the next four alkanes.
The main components of gasoline are heptane, heptane, and octane.
Clean-burning vehicles powered by is crucial for this use because the injection system simply squirts a stream of gasoline natural gas help to reduce air pollution into the air intake as it rushes through.
In urban areas, gasoline would not evaporate easily.