Organic Chemistry Nomenclature: Alkanes

What is Organic Chemistry? Study of hydrocarbons and derivatives 7 million Organic Compounds 1.5 million Inorganic Compounds Animal and plant matter, Foods, Pharmaceuticals, Cosmetics, Fertilizers, Plastics, Petrochemicals, Clothing

Organic Compounds  Contain carbon  Have covalent bonds  Have low melting points  Have low boiling points  Burn in air (oxygen)  Are soluble in nonpolar solvents  Form large molecules

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Crude oil can have different components depending on where in the world it comes from

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How is Crude Oil Refined? Distillation towers Separated by the physical property of … Boiling Point

Boiling Point Trends Small molecules low boiling points usually gases at room temperature Large molecules high boiling points usually liquids and solids at room temperature

Sources of Organic Compounds Fractional Distillation of Crude Oil

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Alkanes Hydrocarbon chains where all the bonds between carbons are SINGLE bondsHydrocarbon chains where all the bonds between carbons are SINGLE bonds sp 3 Hybridized Orbitals– tetrahedral,109.5 osp 3 Hybridized Orbitals– tetrahedral,109.5 o Name uses the ending –aneName uses the ending –ane Examples: Methane, Propane, Butane, Octane, 2-methylpentaneExamples: Methane, Propane, Butane, Octane, 2-methylpentane

IUPAC Names Name# carbons Structural Formula Methane1CH 4 Ethane2CH 3 CH 3 Propane3CH 3 CH 2 CH 3 Butane4CH 3 CH 2 CH 2 CH 3 Pentane5CH 3 CH 2 CH 2 CH 2 CH 3

IUPAC NAMES Name # carbons Structural Formula Hexane 6 CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 Heptane 7 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Octane 8 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Nonane 9 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Decane 10 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3

Prefixes for # of Carbons 1Meth6Hex 2Eth7Hept 3Prop8Oct 4But9Non 5Pent10Dec

More Alkanes H HCondensed Structural Formulas H C C HCH 3 CH 3 H HEthane H H H H C C C HCH 3 CH 2 CH 3 H H H Propane

Learning Check Alk1 A. What is the condensed formula for H H H H H C C C C H H H H H B. What is its molecular formula? C. What is its name?

What is the General formula for Alkanes?

Summary: IUPAC Rules for Alkane Nomenclature Find and name the longest continuous carbon chain. 1. Find and name the longest continuous carbon chain. AKA: parent chain. 2. Number the chain consecutively, starting at the end nearest an attached group (substituent). 2. Number the chain consecutively, starting at the end nearest an attached group (substituent). 3. Identify and name groups attached to this chain. (Examples: methyl-, bromo-, etc.) 3. Identify and name groups attached to this chain. (Examples: methyl-, bromo-, etc.) 4. Designate the location of each substituent group with the number of the carbon parent chain on which the group is attached. Place a dash between numbers and letters. (Example: 3-chloropentane) 5. Assemble the name, listing groups in alphabetical order. The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when alphabetizing. Place a comma between multiple numbers. (Example: 2,3-dichloropropane) 5. Assemble the name, listing groups in alphabetical order. The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when alphabetizing. Place a comma between multiple numbers. (Example: 2,3-dichloropropane)

Step 1. Find the parent chain. Where is the longest continuous chain of carbons?Where is the longest continuous chain of carbons?

Endings Alkanes (all C-C single bonded parent chain) end in –aneAlkanes (all C-C single bonded parent chain) end in –ane –Methane CH 4 –Ethane C 2 H 6 –Propane C 3 H 8 Attached carbon groups (substituents) end in –ylAttached carbon groups (substituents) end in –yl –Methyl CH 3 - –Ethyl CH 3 CH 2 - –Propyl CH 3 CH 2 CH 2 – –Propyl CH 3 CH 2 CH 2 – 3-ethylpentane

Step 2. Number the parent chain. Number the parent chain so that the attached groups are on the lowest numbers Methyl is on carbon #2 of the parent chain Methyl is on carbon #4 of the parent chain GREEN is the right way for this one! Groups on 2, 3, and 5 Groups on 4, 6, and Groups on 2 and Groups on 3 and 6

Step 3. Name the attached groups. Carbon (alkyl) groupsCarbon (alkyl) groups –Methyl CH 3 - –Ethyl CH 3 CH 2 - –Propyl CH 3 CH 2 CH 2 – HalogensHalogens –Fluoro (F-) –Chloro (Cl-) –Bromo (Br-) –Iodo (I-)

Step 4. Designate where the group is attached to the parent chain. Use the numbers of the parent chain from step 2 to designate the location of the attached groups to the parent chain methyl

Step 5. Alphabetize the groups, combine like groups, and assemble. The prefixes di, tri, tetra etc., used to designate several groups of the same kindThe prefixes di, tri, tetra etc., used to designate several groups of the same kind Prefixes are not considered when alphabetizing (Example: dimethyl = m for alphabetizing)Prefixes are not considered when alphabetizing (Example: dimethyl = m for alphabetizing) Parent chain goes LASTParent chain goes LAST 1,1,1-trichloro-1- fluoromethane 1,1-dichloro-1,1- difluoromethane

Draw Some Simple Alkanes 2-methylpentane2-methylpentane 3-ethylhexane3-ethylhexane 2,2-dimethylbutane2,2-dimethylbutane 2,3-dimethylbutane2,3-dimethylbutane

Structural Formulas “Lazy” way to write the Hydrogens Instead of drawing the bonds, just state how many hydrogens are attached NOTE: The bonds are between CARBONS in a parent chain, and not hydrogens! Structural Formula Lewis Structure

Order of Priority IN A TIE, halogens get the lower number before alkyl groupsIN A TIE, halogens get the lower number before alkyl groups 4-chloro-2-methylpentane or 2-chloro-4-methylpentane?

Order of Priority IN A TIE between SIMILAR GROUPS, the group lower ALPHABETICALLY gets the lower numberIN A TIE between SIMILAR GROUPS, the group lower ALPHABETICALLY gets the lower number 4-bromo-2-chloropentane or 2-bromo-4-chloropentane ?

Isomers Straight chain alkanes: Straight chain alkanes: – Alkane with straight carbon back bone Branched chain alkanes: Branched chain alkanes: –Alkane with a branching connection of carbons. Isomers: Isomers: –Same molecular formula but different structures.

Only one possible atom arrangement methane (CH 4 ) ethane (C 2 H 6 )propane (C 3 H 8 )

Butane (C 4 H 10 ): 2 isomers linear alkane or branched alkane linear alkane or branched alkane

Isomers are completely different compounds. Varied Structures Physical properties (MP, BP)

Types of Carbon Atoms Primary carbon (1 o )Primary carbon (1 o ) –a carbon bonded to one other carbon one other carbon Secondary carbon (2 o )Secondary carbon (2 o ) –a carbon bonded to two other carbons two other carbons Tertiary carbon (3 o )Tertiary carbon (3 o ) –a carbon bonded to three other carbons three other carbons

Alkanes Example: Name the following compounds:

Alkanes Example: Write the condensed structure for the following compounds: 3,3-dimethylpentane2-methyl-4-sec-butyloctane1,2-dichloro-3-methylheptane

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