1.1 Alkanes

ORGANIC CHEMISTRY: the study of carbon compounds ORGANIC COMPOUND: a molecular compound of carbon (not including CO (g) , CO2 (g) , and HCN (g))

Why Carbon? carbon can form 4 covalent bonds carbon atoms bond to one another to form chains, rings or sheets carbon can form single, double, or triple bonds Catenation ability “chain making ability”

HYDROCARBONS … are molecules consisting of a chain of carbon to which H’s are attached. They are useful as fuels. Hydrocarbons are the most basic type of molecule in organic chemistry.

ALKANES Alkanes are saturated hydrocarbons meaning they contain only single bonds. All alkanes have a specific prefix and end in “ane” The general formula for an alkane is CnH2n+2

No. OF C ATOMS NAME CONDENSED FORMULA STRUCTURAL FORMULA 1 methane CH4 2 ethane C2H6 3 propane C3H8 4 butane C4H10 5 pentane C5H12 6 hexane C6H14 7 heptane C7H16 8 octane C8H18 9 nonane C9H20 10 decane C10H22

EXAMPLE: OCTANE

CYCLIC ALKANES … contain carbon atoms that can join to form a closed ring. They are also known as cycloalkanes. ex. cyclopropane C3H6 is the simplest cycloalkane. General formula is CnH2n

ALKYL GROUPS An alkyl group is a hydrocarbon branch attached to the main chain. Example: A methyl group (CH3) is a fragment of a methane molecule (CH4) The -yl ending means “a fragment of an alkane formed by removing a hydrogen.”

No. OF C ATOMS ALKYL GROUP CONDENSED FORMULA 1 methyl CH3 2 ethyl C2H5 3 propyl C3H7 4 butyl 5 pentyl 6 hexyl 7 heptyl 8 octyl 9 nonyl 10 decyl

ISOMERS OF ALKYL GROUPS When alkyl groups have three or more C atoms, they may be attached to the parent chain either at the end C atom or at one of the middle C atoms. and... k

RULES FOR NAMING ALKANES ID the longest chain first ID all groups attached to the parent chain (fig 7 p. 11) number the parent chain so that substituents are attached to the C with the lowest number if there is a tie, go alphabetically if the same substituent is present more than once use a prefix to indicate this (di, tri, etc) and include a number to indicate location

FINAL NAME SHOULD INCLUDE: substituents listed in alphabetical order, ignoring prefixes words separated by hyphens numbers separated by commas simple possible arrangement used for parent chain

NAME THE FOLLOWING:

NAME THE FOLLOWING:

NAME THE FOLLOWING: Could be called 5-tert-butyl-8-ethyl-3-methyldecane or 5-(butan-2-yl)-8-ethyl-3-methyldecane

NAME THE FOLLOWING:

RULES FOR DRAWING ALKANES draw the parent chain from the last part of the compound name identify the C atoms to which the substituents are attached draw the substituents attached to the parent chain or ring

Draw the structural formula for 4-ethyl-3,5-dimethylnonane

Draw the structural formula for 7-ethyl-2-methyl-4(propan-2-yl)decane

Draw the structural formula for 1-ethyl-2-propylcyclobutane

PRACTICE TIME! p. 14 1 & 2

PROPERTIES OF ALKANES C-H bonds are nonpolar (En = 0.4) H bonds are evenly arranged so molecules also nonpolar VDW are the main forces at work and since they are weak, they have low MP and BP BP/MP directly related to the length of the chain

FRACTIONAL DISTILLATION

ALKYL HALIDES This is an alkane where a halogen replaces a hydrogen as a substituent group. Alkyl halides are formed by a substitution reaction. Named by writing the root of the halogen name first, followed by “o”, followed by the name of the parent alkane.

NAMING ALKYL HALIDES a) b)

DRAWING ALKYL HALIDES c) 1,1,3-tribromobutane d) 3-bromo-2,5-difluoro-4-ethylheptane

PROPERTIES OF ALKYL HALIDES halogen atom attached to carbon makes for a very polar bond, so alkyl halides are very polar dipole-dipole bonds make for higher boiling points CFC’s (chlorofluorocarbons) used as coolants in refrigerators. They are nontoxic and unreactive. PROBLEM: they destroy the ozone layer!

REACTIONS OF ALKANES generally unreactive at room temperature (ex. with acids, bases, oxidizing agents) used as fuel b/c complete combustion releases a lot of energy long chain vs short chain? Undergo substitution reactions in the presence of UV light and halogens to turn into alkyl halides (or haloalkanes) complete combustion of butane? Substitution reaction between butane and chlorine gas?

HOMEWORK: p. 17 # 1-7