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Getting Started…

• You first have to identify the “family” that your molecule belongs to… IUPAC Nomenclature • So, check for functional groups… Naming Molecules by Following the Rules • If there are none, then your molecule is simply an alkane…

The Three Basic Parts Basic Part - Suffixes

• The name for any organic molecule • Suffixes on the end of the name of an consists of three basic parts: organic molecule tell you what major family the molecule belongs to Prefixes-Parent-Suffix • The suffix for an alkane is “-ane” • Each part of the name has a purpose.

Basic Part – the Parent Parent and suffix…

• The “parent” part of the name tells you • The parent is named based on the how many carbons are in the main chain number of carbons of the molecule • 1 carbon = “meth” • So a one-carbon alkane is called • The main chain of the molecule is methane defined for alkanes as being the longest CH chain in the molecule 4

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Parent and suffix… Parent and suffix…

• 2 carbons = “eth” • 3 carbons = “prop”

• So a two carbon alkane is called ethane. • So a three carbon alkane is called propane.

CH3CH3 CH3CH2CH3

Parent and suffix… And now the rest… • 4 carbons = “but” • 5 carbons = “pent” • 6 carbons = “hex” • So a four carbon alkane is called butane. • 7 carbons = “hept” • 8 carbons = “oct” • 9 carbons = “non” CH3CH2CH2CH3 • 10 carbons = “dec”

• So be brilliant and name the following Answer? alkane (shown as both condensed • That’s right! formula and a skeletal structure) • nine carbons + alkane family = NONANE

CH CH CH CH CH CH CH CH CH 3 2 2 2 2 2 2 2 3 • One more thing - Should you have two or more chains that are the same length, or the parent is the one with the most prefixes… • But - We need to talk Prefixes first… we’ll come back to this…

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Here we go – the Prefixes Prefixes – the Halides

• Prefixes are the bits and pieces that • The family called alkyl halides does not are attached to the main chain (parent) have a suffix. of the molecule. • Halides are always named as prefixes. • An example of a prefix might be a • Fluorine is called “fluoro” halide attached to the main chain as in: • Chlorine is called “chloro” Br • Bromine is called “bromo” • Iodine is called “iodo”

Putting together a name… Now let’s take a look:

• The rules for IUPAC nomenclature • Follow the rules… Name this molecule… include: • Step 1: Find the main chain Br • Step 2: Number the main chain • Step 3: Identify all prefixes and their position numbers • Step 4: Write the full name: Prefixes- Parent-Suffix

Find the main chain… Number the chain…

• The longest chain in this molecule has • This molecule is symmetrical. It doesn’t seven carbons… and only a halide (which matter if we go left to right or right to is always named as a prefix). left… that bromine is attached to carbon #4 Br Br 4 • This will be a heptane.

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Final Answer? What would you do different..?

• If you put the prefix first, then parent • How would you name this one? and suffix, what do you get? Br Br 4 • Number this asymmetric molecule by • “Bromo hept ane” includes all of the beginning your numbering from pieces, except for indicating where the whichever end is closest to the first bromine is attached... substituent (aka: branch, prefix). • 4-bromoheptane is the complete name.

So in this case… Final Answer (again)?

• You would number from left to right, so • 3-bromoheptane the bromine winds up on position #3.

Br Br • If you numbered from the other end, the bromine would be on #5. • Always aim for the lowest possible number on the first substituent!

More Prefixes Alkyl Groups

• The most common prefixes we have in • Alkyl groups are named similarly to organic molecules are those little alkanes, based on the number of carbons fragments of carbon pieces attached to in the fragment. the main chains. • A fragment of methane, CH4, would be • The carbon fragments are called “alkyl CH3- groups”. They all end in “-yl” to indicate • This fragment is called “methyl” where they are fragments of a bigger “meth” stands for one carbon and “yl” molecule. stands for fragment (alkyl group).

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Methyl Group Ethyl Groups

• The molecule shown here has a 7-carbon • A two-carbon alkane is called ethane, main chain. CH3CH3. The corresponding two-carbon

fragment is always CH3CH2-, which is called “ethyl”. • Notice that it has a branch attached to carbon #4. This branch has a single carbon – a methyl group. • 4-methylheptane is the name of this • 4-ethylheptane is the name for this one. compound.

Propyl Groups Isopropyl Groups

• There are two possible three-carbon • There are two possible three-carbon alkyl groups to form from propane, alkyl groups to form from propane,

CH3CH2CH3. CH3CH2CH3.

• The straight chain version: CH3CH2CH2- • The other possibility is to form the which is called “propyl” or “n- fragment on the central carbon:

propyl” (where n stands for “normal” or CH3CHCH3, which is called “isopropyl” straight-chained)

Butyl Groups Sec-Butyl Groups

• There are two possible four-carbon • The other possibility is to form the alkyl groups to form from butane, fragment one of the central carbons:

CH3CH2CH2CH3. CH3CHCH2CH3, which is called “sec- • One possibility is to form the fragment butyl”. [Note that the carbon second on one of the end carbons: from the left only has three bonds – so that’s where its bonding to the main CH3CH2CH2CH2-, which is called “butyl” or “n-butyl” chain]

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Isobutyl Groups Tert-butyl Groups

• There are two other possible four- • The other is formed as a fragment on

carbon alkyl groups to form from the one central carbon, (CH3)3C-, which isobutane, (CH3)3CH. is called “tert-butyl” • One is formed as a fragment on one of the three symmetrical end carbons:

(CH3)2CH(CH2)-, which is called “isobutyl”

What alkyl groups do you see? What alkyl groups do you see?

• There’s two groups attached to the ring • The group in red has two carbons and is below. What are they? an ethyl group. • The group in blue has four carbons. Three in a row and the extra attached at the middle carbon. Its an isobutyl group.

What alkyl groups do you see? What alkyl groups do you see?

• There’s two groups attached to the ring • The group in red has three carbons below. What are they? attached at the middle carbon and is an isopropyl group. • The group in blue has four carbons, in a row, attached at one of the middle carbons. It’s a sec-butyl group.

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More about Prefixes… Alphabetizing Prefixes…

• Every prefix needs a position number… • Sec-butyl and tert-butyl both have a • And prefixes are always alphabetized by descriptive prefix that tells you the their first letter: structure of those alkyl groups... (the – Methyl is an “m” prefix has a prefix!) – Ethyl is an “e” • When alphabetizing, we do NOT use – Propyl is a “p” these descriptive prefixes (like sec- or – Isopropyl is an “i” tert-) to alphabetize… – Sec-butyl is a “b”… (Say what??)

Continuing with Prefixes… Continuing with Prefixes…

• If you have multiples of the same • Di-, tri- and tetra- are more prefixes prefixes, like two bromines in the same for the prefixes. molecule, you COULD name them • Remember - when alphabetizing for separately or you could combine them names, prefixes are never alphabetized into a single prefix name and include using a “prefix” like di- or sec-. “di-” in front to indicate TWO of them. – Sec-butyl is a “b” Br • 3,4-dibromohexane! – Dimethyl is a “m”

Br

Name the following molecule: And the answer is…?

• Keeping all of the rules in mind, what • Longest chain: nine carbons would you name this molecule: • Number: left to right (hit that first branch on #4)

• 4 Group on #4 is methyl. 5 • Group on #5 is isopropyl. • Alphabetize! • 5-isopropyl-4-methylnonane.

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About that main chain again… Where’s the Parent?

• Recall that we said if you had two chains • There are two options: Option 1 is the same length, the parent is the one highlighted in red: with the most branches. Which is the parent in this example? • Option 2 is highlighted in blue:

And the winner is… Finally… the name…

• The red one has two branches: • Eight carbons in main chain. Octane. • Number left to right (first branch on #2!) • Three alkyl groups attached: 6 • The blue one has three branches: • 2-methyl 2 • 5-propyl 5 • 6-methyl • The blue one is the parent. • Simplify prefixes by using 2,6-dimethyl • Write that name… • Full name: 2,6-dimethyl-5-propyloctane.

The last kind of alkyl groups – Naming Complex Branches Complex Branches • Complex branches are those that have • Find the point of attachment inside the no simple name, yet they still need to be complex branch itself, first. named.

• Identify the complex branch and its point of attachment.

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Naming Complex Branches Naming Complex Branches

• Number the longest branch of that • Identify the prefixes on that little complex branch, starting from the point miniature parent (in this case, the of attachment, #1. In this case, propyl propyl chain) of the complex branch, and is the miniature parent. their position numbers. • In this example, there are two methyls 2 3 1 attached to #1. 2 3 1

Naming Complex Branches Now: Cyclic Compounds

• Write the full name, placing the complex • When naming cyclic compounds, first branch inside brackets. This complex determine if the ring is the parent, or branch is attached to #5 of the original not. main chain so: • If the ring has more carbons than any • 5-[1,1-dimethylpropyl]nonane is the of the alkyl groups attached, the ring is name. 2 the parent. 3 1 • If not, the ring becomes a cycloalkyl group and is a prefix for the main chain.

Cyclic Compounds – Parent? Cyclic Compounds

• In this example, the ring has four • In this example, the ring has five carbons carbons and the chain has eight. and the alkyl group has three.

• The five-carbon ring is the parent and is • The chain is the parent and the ring is a called cyclopentane. prefix. • The one alkyl group will be on #1 (of • The ring is a cyclobutyl group on #1. course – that #1 isn’t even needed!) • Propylcyclopentane is the name. • 1-cyclobutyloctane.

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Cyclic Compounds – Multiple Cyclic Compounds Groups • Word of caution: don’t double dip… its • When a ring has multiple groups, the really easy to double count the carbon rule for numbering is: “Number around (*) that the alkyl group is attached to. the ring so as to arrive at the lowest • Alkyl groups are only those BEYOND possible sum of the position numbers”. the ring carbons. Thus, this is a propyl • The sum in this molecule is 1 + 3 = 4. group not a butyl group. 1 1 3 * 3 2

Cyclic Compounds – Multiple Cyclic Compounds – Multiple Groups Groups • How about this one? • Lowest possible sum?

4

1 2

• 1 + 2 + 4 = 7

Cyclic Compounds – Multiple Cyclic Compounds – Multiple Groups Groups • If you have two possibilities for lowest • Two possible “lowest sums” of 4, where possible sum, THEN (and only then) you the groups must be on carbons #1 and should alphabetize to prioritize your #3. groups. • Prioritize by alphabetizing – the ethyl • What about this one? will be #1 and the isopropyl will be #3.

• Name? 1-ethyl-3-isopropylcyclopentane

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Cyclic Compounds – Two groups Cyclic Compounds – Two groups

• Last comment – when you have two groups attached to a molecule, they can potentially either both face up (or down) in the same direction (CIS) or one CIS TRANS faces up and the other faces down (TRANS) • The molecule on the left has two methyl • We use wedges to indicate “up” or groups facing down (CIS) and the one on towards you and dashes for “down” or the right has one down and one up away. (TRANS).

Cyclic Compounds – Two groups Finale

• Incorporating that into the name: Place • I think this covers everything that you the term “cis” or “trans” in the should know and be able to do for beginning of the name, before the first naming basic alkanes and cycloalkanes.

prefix • As we add more families (alkenes,

alkynes, etc) we will build on this “foundation” of nomenclature rules… • Good luck… • Name? CIS-1,2-dimethylcyclohexane

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