Organic Nomenclature

C Expected Lewis Structure of Carbon: Problems: 4 valence electrons Allows 2 orbitals for covalent bonding Can’t fill octet rule C

ORBITAL HYBRIDIZATION - s and p orbitals combine to form an even distribution of electrons around the nucleus Redraw Lewis Dot Structure allows for the formation of 4 covalent bonds

IMPORTANCE: Allows carbon to form complex structures - many being biological compounds Organic Chemistry: study of compounds containing Carbon (except CO2 and CO)

Types of Formulas 1. Chemical - Empirical: Reduced Form - Molecular: Non-Reduced Form 2. Structural - shows the location and bond types of each atom 3. Compact Structural - shows the groupings of atoms around the carbons

Example Butane: Molecular: C4H10 Empirical: C2H5 Structural: Compact Structural: CH3CH2CH2CH3 or CH3(CH2)2CH3

Ethane Molecular Formula: C2H6 Empirical Formula: CH3

Ethane Molecular Formula: C2H6 Empirical Formula: CH3 Lewis Dot Diagram:

Ethane Molecular Formula: C2H6 Empirical Formula: CH3 Lewis Dot Diagram: Structural Formula: Compact Structural Formula: CH3CH3

Ethene Molecular Formula: C2H4 Empirical Formula: CH2

Ethene Molecular Formula: C2H4 Empirical Formula: CH2 Lewis Dot Diagram:

Ethene Molecular Formula: C2H4 Empirical Formula: CH2 Lewis Dot Diagram: Structural Formula: Compact Structural Formula: CH2CH2

Ethyne Formula: C2H2 Empirical Formula: CH

Ethyne Formula: C2H2 Empirical Formula: CH Lewis Dot Diagram:

Ethyne Formula: C2H2 Empirical Formula: CH Lewis Dot Diagram: Structural Formula: Compact Structural Formula: CHCH

Importance Structure and Function: differences in structure, even slight, change the properties - absorption site, metabolism, and effects differences must be indicated in the names = Nomenclature

NOMENCLATURE: process of naming 1st step: # of carbons determines the base or root name # of Carbons Root Name 1 Meth 11 Undec 2 Eth 12 Dodec 3 Prop (“rope”) 13 Tridec 4 But (“cute”) 14 Tetradec 5 Pent 15 Pentadec 6 Hex 20 Icos 7 Hept 21 Henicos 8 Oct 22 Docos 9 Non (“known”) 30 Triacont 10 Dec 40 Tetracont

2nd step: identify types of bonds Saturated - all carbons are single bonded to one another and contain all possible hydrogens (full of H) Unsaturated - two or more carbons are double or triple bonded to one another - decreases the # of hydrogens

Saturated – all single bonds - ending is “ane” Unsaturated: at least one double or triple bond - double bond “ene” - triple bond “yne”

Examples:

Examples: Butane

Condensed Formula

Pentene

Simplified Structural Form 4 2 1 5 3 Double Bond

Propyne

Propyne

SAME???? NO – bond is in a different position HOWEVER: Formula: C4H8 Formula: C4H8 SAME???? NO – bond is in a different position - ISOMER: same chemical formula, but different STRUCTURE

SAME???? NO – bond is in a different position HOWEVER: 2 – Butene 1-Butene Formula: C4H8 Formula: C4H8 SAME???? NO – bond is in a different position - ISOMER: same chemical formula, but different STRUCTURE

Types of Isomers 1. Positional Isomers: - differ by position of double or triple bonds 2. Geometric Isomers: - differ by the orientation around a double bond 3. Structural Isomers: - differ due to side chains

Positional Isomers CΞC-C-C-C C-C-C-C=C-C difference in location of double or triple bond Name based on position of the different bond (double or triple): RULE: - number the carbon chain so the bond has the smallest “address” - list the number in front of the root name with the appropriate ending - separate the number from the root name with a dash EXAMPLES: CΞC-C-C-C C-C-C-C=C-C 3-hexene 3-octyne What should 3-pentene be called?

More than one double/triple bond: RULE: The carbon chain is numbered unidirectionally so that each bond has the lowest possible combination of addresses list each address number separated by commas add a prefix before the bond suffix to indicate the number of double or triple bonds   EXAMPLES: C-C=C-C=C-C-C C-CΞC-CΞC-CΞC-C 1,3,5-heptatriene 2,5-octadiyne

Mix of double and triple bonds RULE: Number to give smallest addresses – if no difference “ene” has priority. Name in this order: Double bond address # – carbon chain root name“ene” – triple bond address # - “yne” If there are multiple double/triple, follow those rules as well

Examples C-C=C-CΞC C=C-C=C-CΞC-C-C C-C=C-CΞC-CΞC-C-C-C C-C=C-CΞC-C 4-hexene-1-yne

Geometric Isomers Difference based on the orientation around a double bond Two possibilities can result due to rotational restriction by the double bond If the groups are on the same side of the double bond = cis If the groups are on the opposite side of the double bond = trans

Geometric Isomers Difference based on the orientation around a double bond Two possibilities can result due to rotational restriction by the double bond If the groups are on the same side of the double bond = cis If the groups are on the opposite side of the double bond = trans cis - 2-butene trans - 2- butene

Structural Isomer: different assembly of carbons – side chains RULE: Name parent chain and side chains based on position Process: 1. Name parent chain - count longest chain = parent chain = base - chain must include double or triple bonds - if more than one double/triple bond, number them so both bonds have the lowest possible number - if double and triple bonds, triple bonds have priority so it should have the lowest number 2. Name Side Chain(s) - count carbons in side chain and name appropriately - # of carbons in side chain = name of side chain - add ”yl” suffix

Examples

More than One Side chain: each side chain gets its own number (even if on the same carbon of parent chain) if more than one of the same type of side branch add pre-fix to the side chain’s root name “di” = two of the same side chain “tri” = three of the same side chain “tetra” = four of the same side chain list the side chains and their numbers before the name of the parent chain – separate numbers with commas Different types of side chains are listed in alphabetical order of the root of the side chain (butyl before ethyl before methyl before pentyl…) , but not by the “di, tri, tetra prefix”,

Examples

Branched Side Chains

Naming Halogenated Compounds Halogens: - column next to the Noble Gases – F, Cl, Br, I - acts as a side chain (same numbering rules), but instead of “yl” as the ending, add an “o” F - fluoro Cl - chloro Br - bromo I - iodo

Examples

Naming Ring Structures Ring structures are represented by geometric shapes where each angle represents a carbon Add a “cyclo” in front of the name and use the root for the number of angles and the proper ending (ane or ene – no yne)

Rules for side chains and double bonds 1. Double bonds have priority. The bonds must be numbered with the smallest address but the numbering determines the direction around the ring. 4 3 2 1 6 5 1 6 5 4 3 2 6 1 2 3 4 5

Rules for side chains and double bonds Double bonds have priority. The bonds must be numbered with the smallest address but the numbering determines the direction around the ring. 4 3 2 1 6 5 1 6 5 4 3 2 6 1 2 3 4 5

4 3 2 1 6 5 1 2 3 4 5 6

4 3 2 1 6 5 1 2 3 4 5 6 1,3-cyclohexadiene

Rule for Ring Structures with Side Chains 2) if no double bonds, number the side chains so they have the lowest address 3) same naming as before

Examples

What if the side chain is bigger than the ring structure? If the number of carbons in the ring is greater than the number of carbons on the largest side chain, then the parent name is based on the ring structure. If the number of carbons on the straight chain is larger than the number of carbons in the ring structure, the parent name is based on the straight chain and the ring structure is treated as a side chain - Rule: add a “yl” to the ring structure name 2-cyclopropylhexane vs. propylcyclohexane

A special case: Benzene 1,3,5-cyclohexatriene

Benzene Resonance

Naming Benzene Compounds Rules: Benzene is the base name. Number side chains and/or halogens to give them the smallest address. If it’s a di-substituted (2 side chains), the following roots can be used: 1,2 = ortho or o 1,3 = meta or m 1,4 = para or p

Examples

Benzene Derivatives

Benzene as a Side Chain Use the word “Phenyl”

https://people.ok.ubc.ca/pshipley/teaching/chem203/worksheets/nomenclature.pdf