6_Alkanes_P1.pdf

MBIOL 112 ALKANES http://www.free-powerpoint-templates-design.com  At the end of this module, you should OBJECTIVES have achieved the following topic learning outcomes: 1. Draw the structure or isomers of alkanes, cycloal...

MBIOL 112 ALKANES http://www.free-powerpoint-templates-design.com  At the end of this module, you should OBJECTIVES have achieved the following topic learning outcomes: 1. Draw the structure or isomers of alkanes, cycloalkanes, bicycloalkanes, and alkyl halides from their names. 2. Name alkanes, cycloalkanes, bicycloalkanes, and alkyl halides with the given structure. 3. Evaluate the trends in the physical properties of alkanes, cycloalkanes, bicycloalkanes, and alkyl halides. 4. Predict the most stable conformations of alkanes and cycloalkanes.  Hydrocarbons most basic type of organic molecules they are comprised of only 2 elements: hydrogen and carbon. have one or more central carbon atoms in a branched or chain-like structure, surrounded by hydrogen atoms four main categories of hydrocarbons: Alkanes, Alkenes, Alkynes, and Aromatic hydrocarbons Hydrocarbons  Alkanes aliphatic hydrocarbon that contains only a single bond simplest and least reactive than other classes of hydrocarbons poor acids and bases, poor electrophiles and nucleophiles  Alkanes (CnH2n+2) Give the molecular formula given the value of n: a) n=1 b) n=2 c) n=3 d) n=4 Alkanes (CnH2n+2) Naming Alkanes: straight-chain/normal alkanes Naming Alkanes: straight-chain/normal alkanes Naming Alkanes: straight-chain/normal alkanes named according to the number of carbon atoms they contain the suffix -ane is added to the end of each name to indicate that the molecule identified is an alkane Naming Alkanes: branched-chain alkanes Naming Alkanes: branched-chain alkanes Isomers (from the Greek isos + meros, meaning “made of the same parts”) compounds that have the same numbers and kinds of atoms (molecular formula) but differ in the way the atoms are arranged (structural formula) constitutional isomers Naming Alkanes: branched-chain alkanes Regardless of the reason for the isomerism, constitutional isomers are always different compounds with different properties but with the same formula. Naming Alkanes: branched-chain alkanes Naming Alkanes: branched-chain alkanes Naming Alkanes: branched-chain alkanes  Naming Alkanes: branched-chain alkanes International Union of Pure and Applied Chemistry (IUPAC) Rules: 1) The Main Chain: Give the base name of the compound Find the longest continuous chain of carbon atoms, and use the name of this chain as the base name of the compound, ending with -ane. When there are two longest chains of equal length, use the chain with the greater number of substituents as the main chain.  Naming Alkanes: branched-chain alkanes 6 - hexane  Naming Alkanes: branched-chain alkanes 2) Numbering The Main Chain: Give locations of the substituents, assign a number to each carbon atom in the main chain Number the longest chain, beginning with the end of the chain nearest a substituent.  Naming Alkanes: branched-chain alkanes 6 - hexane  Naming Alkanes: branched-chain alkanes 3) Naming Alkyl Groups: Name the substituent groups Name the substituent attached to the longest chain as alkyl groups. Give the location of each alkyl group by the number of the main-chain carbon atom to which it is attached. Alkyl groups are named by replacing the -ane suffix of the alkane name with -yl. Naming Alkanes: branched-chain alkanes 2 methyl 2 methyl 4 ethyl  Naming Alkanes: branched-chain alkanes 6 C atoms - hexane Substituents: 2 methyl 2 methyl 4 ethyl *Alkyl - arrange alphabetically Name: 4-ethyl,2,2-dimethylhexane  Naming Alkanes: branched-chain alkanes Halogen substituents are named fluoro-, chloro-, bromo-, and iodo-. 1. 2. 3. 4. 5. 6. ALKYL GROUPS ALKYL GROUPS 4-isopropyloctane, 5-tert-butyldecane *note: alphabetical arrangement not considered: – sec, tert – di, tri, tetra, etc. considered: – iso – ex. isobutyl, isopropyl, propyl (correct order) CYCLOALKANES (CnH2n) contain rings of carbon atoms Physical properties: Nonpolar Physical properties are similar to those of the compact, branched alkanes CYCLOALKANES (CnH2n) Nomenclature (naming) of Cycloalkanes Simple cycloalkanes are named with the prefix cyclo-, indicating the presence of a ring. 1. If there is just one substituent, no numbering is needed.  2. Numbering begins with one of the substituted ring carbons and continues in the direction that gives the lowest possible numbers to the other substituents. Begin the numbering with the one that has more substituents.  * When two or more different alkyl groups that could potentially receive the same numbers are present, number them by alphabetical priority, ignoring numerical prefixes such as di- and tri-.  *If halogens are present, treat them just like alkyl groups.  3. When the acyclic portion of the molecule contains more carbon atoms than the cyclic portion (or when it contains an important functional group), the cyclic portion is sometimes named as a cycloalkyl substituent.  Bicyclic Alkanes contain more than one ring with at least two common atoms the common atoms connecting the rings in a bicyclic compound are called bridgehead carbons fused - adjacent bridgehead carbon atoms bridged - not adjacent bridgehead carbon atoms  Nomenclature 1. Start counting C atoms from the bridgehead of the “bigger” ring. total number of C atoms = ,  Nomenclature 2. “bicyclo” followed by a square bracket with the number of carbon atoms in each ring 3 rings Example Bicycloalkanes with substituents Bicycloalkanes with substituents  Name the following: 1. 2. 3.