Organic Chemistry Nomenclature Alkanes What is Organic Chemistry

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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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 bonds • sp 3 Hybridized Orbitals– tetrahedral, 109. 5 o • Name uses the ending –ane • Examples: Methane, Propane, Butane, Octane, 2 -methylpentane

IUPAC Names Name # carbons Structural Formula Methane 1 CH 4 Ethane CH 3 2 Propane 3 CH 3 CH 2 CH 3 Butane CH 3 CH 2 CH 3 4 Pentane 5 CH 3 CH 2 CH 2 CH 3

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

Prefixes for # of Carbons 1 Meth 6 Hex 2 Eth 7 Hept 3 Prop 8 Oct 4 But 9 Non 5 Pent 10 Dec

More Alkanes H H Condensed Structural Formulas H C C H H H H H C C C H H H H CH 3 Ethane CH 3 CH 2 CH 3 Propane

Learning Check Alk 1 A. What is the condensed formula for H H H C C 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 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). 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)

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

Endings • Alkanes (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 –yl – Methyl CH 3 – Ethyl CH 3 CH 2– Propyl CH 3 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 1 2 3 4 5 4 3 2 1 GREEN is the right way for this one! 1 8 7 2 3 7 8 6 2 1 4 5 6 5 4 3 Groups on 4, 6, and 7 Groups on 2, 3, and 5 1 2 3 4 5 6 7 6 5 4 3 2 7 1 Groups on 2 and 5 Groups on 3 and 6

Step 3. Name the attached groups. • Carbon (alkyl) groups – Methyl CH 3 – Ethyl CH 3 CH 2– Propyl CH 3 CH 2 – • Halogens – 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. 2 -methyl 1 2 3 4 5

Step 5. Alphabetize the groups, combine like groups, and assemble. • The 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) • Parent chain goes LAST 1, 1, 1 -trichloro-1 fluoromethane 1, 1 -dichloro-1, 1 difluoromethane

Draw Some Simple Alkanes • 2 -methylpentane • 3 -ethylhexane • 2, 2 -dimethylbutane • 2, 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 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 number 4 -bromo-2 -chloropentane or 2 -bromo-4 -chloropentane ?

Isomers • Straight chain alkanes: – Alkane with straight carbon back bone • Branched chain alkanes: –Alkane with a branching connection of carbons. • 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

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

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

Alkanes Example: Name the following compounds:

Alkanes Example: Write the condensed structure for the following compounds: 3, 3 -dimethylpentane 2 -methyl-4 -sec-butyloctane 1, 2 -dichloro-3 -methylheptane

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