Self-hand Outs in Chemistry

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ALKANES

The following table contains the systematic names for the first twenty straight chain alkanes. It will beimportant to familiarize yourself with these names, as

they will be the basis for naming many other organicmolecules throughout your course of study.

Names ofxx Straight Chain Alkanes

NameMolecular Formula

Methane CH4

Ethane C2H6

Propane C3H8

Butane C4H10

Pentane C5H12

Hexane C6H14

Heptane C7H16

Octane C8H18

Nonane C9H20

Decane C10H22

Undecane C11H24

Dodecane C12H26

Tridecane C13H28

Tetradecane C14H30

Pentadecane C15H32

Hexadecane C16H34

Heptadecane C17H36

Octadecane C18H38

Nonadecane C19H40

Eicosane C20H42

Alkyl Groups

Alkanes can be described by the general formulaCnH2n+2. An alkyl group is formed by removing onehydrogen from the alkane chain, and is described bythe formula CnH2n+1. The removal of this hydrogenresults in a stem change from -ane to -yl. Take a lookat the following examples. The same concept can beapplied to any of the straight chain alkane namesprovided in the table above.

Using Common Names with Branched Alkanes

Some branched alkanes have common names that arestill widely used today. These common names makeuse of prefixes such as iso- , sec- , tert- , andneo- . Theprefix iso- , which stands for isomer, is commonly givento 2-methyl alkanes. In other words, if there is methylgroup located on the second carbon of a carbon chain,

we can use the prefix iso- . The prefix will be placed infront of the alkane name that indicates the total number of carbons.

Examples to use

isopentane which is the same as 2-methylbutane

isobutane which is the same as 2-methylpropane

To assign the prefixes sec- , which stands for secondary, and tert- , for tertiary, it is important that wefirst learn how to classify carbon molecules. If a carbonis attached to only one other carbon, it is calleda primary carbon. If a carbon is attached to two other carbons, it is called a seconday carbon.Atertiary carbon is attached to three other carbons andlast, a quaternary carbon is attached to four other carbons.

Examples to use

4-sec -butylheptane (30g)

4-tert -butyl-5-isopropylhexane (30d); if using thisexample, may want to move sec/tert after iso disc

The prefix neo-

Examples to use

neopentane

neoheptane

Alkoxy Groups

Alkoxides consist of an organic group bonded to anegatively charged oxygen atom. In the general form,they are written as RO-, where R represents the organicsubstituent. Similar to what we saw with alkyl groupsabove, the concept of naming alkoxides can be appliedto any of the straigt chain alkanes provided in the tableabove.

Three Basic Principles of Naming

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1. Choose the longest, most substituted carbon chaincontaining a functional group.

2. A carbon bonded to a functional group must havethe lowest possible carbon number. If there are nofunctional groups, then any substitute presentmust have the lowest possible number.

3. Take alphabetical order into consideration; that is,

after applying the first two rules given above,make sure that your substitutes and/or functionalgroups are written in alphabetical order.

Example

Rule #1 Choose the longest, most substituted carbonchain containing a functional group. This example doesnot contain any functional groups, so we only need tobe concerned with choosing the longest, mostsubstituted carbon chain. The longest carbon chain hasbeen highlighted in red and consists of eight carbons.

Rule #2 Carbons bonded to a functional group musthave the lowest possible carbon number. If there are nofunctional groups, then any substitute present musthave the lowest possible number. Since this exampledoes not contain any functional groups, we only need tobe concerned with the two substitutes present, that is,the two methyl groups. If we begin numbering the chainfrom the left, the methyls would be assigned the

numbers 4 and 7, respectively. If we begin numberingthe chain from the right, the methyls would be assignedthe numbers 2 and 5. Therefore, to satisfy the secondrule, numbering begins on the right side of the carbonchain as shown below. This gives the methyl groups thelowest possible numbering.

In this example, there is no need to utilize the third rule.Since the two substitutes are identical, neither takesalphabetical precedence with respect to numbering thecarbons. This concept will become more clear in thenext example.

Example

Rule #1 Choose the longest, most substituted carbonchain containing a functional group. This examplecontains two functional groups, bromine and chlorine.The longest carbon chain has been highlighted in redand consists of seven carbons.

Rule #2 Carbons bonded to a functional group musthave the lowest possible carbon number. If there are nofunctional groups, then any substitute present musthave the lowest possible number. In this example,numbering the chain from the left or the right wouldsatisfy this rule. If we number the chain from the left,bromine and chlorine would be assigned the secondand sixth carbon positions, respectively. If we number the chain from the right, chlorine would be assigned thesecond position and bromine would be assigned thesixth position. In other words, whether we choose tonumber from the left or right, the functional groupsoccupy the second and sixth positions in the chain. Inorder to select the correct numbering scheme, we needto utilize the third rule.



Rule #3 After applying the first two rules, takealphabetical order into consideration. Alphabetically,bromine comes before chlorine. Therefore, bromine isassigned the second carbon position and chlorine isassigned the sixth carbon position.

Example

Rule #1 Choose the longest, most substituted carbonchain containing a functional group. This examplecontains two functional groups, bromine and chlorine,and one substitute, the methyl group. The longestcarbon chain has been highlighted in red and consistsof seven carbons.

Rule #2 Carbons bonded to a functional group musthave the lowest possible carbon number. After takingfunctional groups into consideration, any substitutespresent must have the lowest possible carbon number.This particular example illustrates the point of

difference principle. If we number the chain from theleft, bromine, the methyl group and chlorine wouldoccupy the second, fifth and sixth positions,respectively. This is illustrated in the second drawingbelow. If we number the chain from the right, chlorine,the methyl group and bromine would occupy thesecond, third and sixth positions, respectively. This isillustrated in the first drawing below. The position of the

methyl, therefore, becomes a point of difference. Inthe first drawing it occupies the third position. In thesecond drawing it occupies the fifth position. To satisfythe second rule, we want to choose the numberingscheme that provides the lowest possible numbering of this substitute. Therefore, the first of the two carbonchains shown below is correct.

So the first numbering scheme is the one to use

Once you have determined the correct numbering of the carbons, it is often useful to make a list includingfunctional groups, substitutes, as well as the name of the parent chain.

Parent chain: heptane 2-Chloro 3-Methyl 6-Bromo

6-bromo-2-chloro-3-methylheptane

Problems



Alkenes: Nomenclature

Alkenes are normally named using the IUPAC system. The

rules for alkenes are similar to those used for alkanes. The

following rules summarize alkene nomenclature.

1. Identify the longest continuous chain of carbon

atoms that contains the carbon-carbon double bond.

The parent name of the alkene comes from the

IUPAC name for the alkane with the same number

of carbon atoms, except the -ane ending is changed

to -ene to signify the presence of a double bond. For

example, if the longest continuous chain of carbon

atoms containing a double bond has five carbon

atoms, the compound is a pentene.

2. Number the carbon atoms of the longest continuous

chain, starting at the end closest to the double bond.

Thus,

3. is numbered from right to left, placing the double

bond between the second and third carbon atoms of

the chain. (Numbering the chain from left to right

incorrectly places the double bond between the third

and fourth carbons of the chain.)

4. The position of the double bond is indicated by

placing the lower of the pair of numbers assigned to

the double-bonded carbon atoms in front of the

name of the alkene. Thus, the compound shown in

rule 2 is 2-pentene.

5. The location and name of any substituent molecule

or group is indicated. For example,

6. is 5-chloro-2-hexene.

7. Finally, if the correct three-dimensional relationship

is known about the groups attached to the double-

bonded carbons, the cis or trans conformation label

may be assigned. Thus, the complete name of the

compound in rule 4 (shown differently here)

8. is cis-5-chloro-2-hexene.



Compounds containing just carbons and hydrogens arethe most basic compounds encountered in organicchemistry. These compounds are referred to ashydrocarbons. On the most basic level, hydrocarbonscan be divided into three groups: those containing justsingle bonds, those containing one or more doublebonds, and those containing one or more triple bonds.

Before discussing how to name these compounds, it isinstructive to examine how they are represented bychemists.

D r a w i n g H y d r o c a r b o n s

Recall that when carbon makes four bonds, it adopts

the tetrahedral geometry. In the tetrahedral geometry, only

two bonds can occupy a plane simultaneously. The other

two bonds point in back or in front of this plane. In order to

represent the tetrahedral geometry in two dimensions, solid

wedges are used to represent bonds pointing out of the

plane of the drawing toward the viewer, and dashed wedges

are used to represent bonds pointing out of the plane of the

drawing away from the viewer. Consider the following

representation of the molecule methane:

Two dimensional representation of methane

In the above drawing, the two hydrogens connected by

solid lines, as well as the carbon in the center of the

molecule, exist in a plane (specifically, the plane of the

computer monitor / piece of paper, etc.). The hydrogen

connected by a solid wedge points out of this plane toward

the viewer, and the hydrogen connected by the dashed

wedge points behind this plane and away from the viewer.

In drawing hydrocarbons, it can be time-consuming to

write out each atom and bond individually. In organic

chemistry, hydrocarbons can be represented in a shorthand

notation called a skeletal structure. In a skeletal structure,

only the bonds between carbon atoms are represented.

Individual carbon and hydrogen atoms are not drawn, and

bonds to hydrogen are not drawn. In the case that the

molecule contains just single bonds (sp3 bonds), these

bonds are drawn in a "zig-zag" fashion. This is because in

the tetrahedral geometry all bonds point as far away from

each other as possible, and the structure is not linear.

Consider the following representations of the molecule

propane:

Full structure of propane Skeletal structure of propane

Only the bonds between carbons have been drawn,

and these have been drawn in a "zig-zag" manner. Note that

there is no representation of hydrogens in a skeletal

structure. Since, in the absence of double or triple bonds,

carbon makes four bonds total, the presence of hydrogens is

implicit. Whenever an insufficient number of bonds to a

carbon atom are specified in the structure, it is assumed that

the rest of the bonds are made to hydrogens. For example, if

the carbon atom makes only one explicit bond, there are

three hydrogens implicitly attached to it. If it makes two

explicit bonds, there are two hydrogens implicitly attached,

etc. Note also that two lines are sufficient to represent three

carbon atoms. It is the bonds only that are being drawn out,

and it is understood that there are carbon atoms (with three

hydrogens attached!) at the terminal ends of the structure.



A l k a n e n o m e n c l a t u r e

When hydrocarbons contain only single bonds, they are

called alkanes. Alkanes are named using a prefix for the

number of carbon atoms they contain, followed by the suffix

-ane. The following table lists the rules for naming alkanes.

Numb

er of

carbo

n

atoms

Prefi

x

Compou

nd nameImage

1Meth

-Methane

2 Eth- Ethane

3Prop

-Propane

4 But- Butane

5

Pent

- Pentane

6 Hex- Hexane

7Hept

-Heptane

8 Oct- Octane

9 Non- Nonane

Alkane nomenclature is straightforward; the only

difficulties come if one of the hydrogen or carbon atoms on

the molecule is replaced by another atom or group. When

this takes place, the group which replaces the hydrogen or

carbon is called a substituent.

Since the only kind of molecules we've discussed so far

are alkanes, let's consider the situation in which one of the

hydrogen atoms on an alkane has been replaced by another

alkane. Consider the following molecule, 3-methypentane:

Skeletal structure of 3-methylpentane

Consider the long chain of five carbon atoms at the top

of the image. If this were all that composed the molecule, it

would simply be called pentane. However, one of the

hydrogens on the carbon third from the end has been



replaced with an alkane, specifically methane. How are we

to name this molecule?

1. First, we identify the longest chain of carbon

atoms. We name this alkane. It will serve as the

root name for the molecule.

○ In the example above, the root name is

pentane.

2. Next, we number the carbon atoms, starting at the

end that gives the substituent the lowest number.

○ In the example above, we can count

from either end and arrive at 3 for the

substituent.

3. Next, we name the substituent as if it were an

independent alkane. However, we replace suffix

-ane with -yl. This name will serve as the prefix.

○ In the example above, methane is the

substituent, so we call it methyl.

4. The compound is named "number-

prefixrootname".

○ In the example above, the name is 3-

methylpentane

Let's try some more complicated examples. What

happens if the alkane has more than one substituent? In this

case, the rules above are followed, and the carbons on the

longest chain are numbered to give the lowest number

possible to one of the substituents. The substituents are then

all named in the prefix, separated by a dash, in alphabetical

order (e.g. 3-ethyl-2-methyl). If the same substituent is

attached several times, the numbers of all carbon atom to

which it is attached are repeated, separated by commas,

before it to indicate the number of substituents. In addition,

the prefixes di- (2), tri- (3), or tetra- (4) are used. The

prefixes are ignored when considering alphabetical order.

Consider the following compound:

Skeletal structure of 4-ethyl-2,2-dimethylheptane

The longest carbon chain has seven carbon atoms, so

the root name is heptane. Numbering from the right gives the

lowest number to the first substituent. There are two methyl

substituents at the second carbon atom, so we use the prefix

2,2-dimethyl. There is another substituent on the fourth

carbon atom, so we use the prefix ethyl. Ethyl comes before

methyl alphabetically, so we name the compound 4-ethyl-

2,2-dimethylheptane.

Let's consider one final example, when the substituent

is not a linear alkane. If the substituent is branched, we

consider these branches to be substituents of the original

substituent (confused yet?). The substituent's substituents

must be named using the rules outline above. The final

name of the original substituent is placed in parentheses.

Consider the following molecule:



Skeletal structure of 5-(1-methylpropyl)nonane

The longest chain of carbon atoms is clearly located at

the bottom of the molecule. This chain gives it the root name

nonane. The substituent is located at the second carbon

atom. The substituent, however, is branched. If we were to

name it alone, we would call it 1-methylpropane. But it is a

substituent, so we must use the suffix -yl. The molecule is

named 5-(1-methylpropyl)nonane.

A l k e n e n o m e n c l a t u r e

Alkenes are hydorcarbons containing one or more

double bonds. Alkenes are named using the same general

naming rules for alkanes, except that the suffix is now -ene.

There are a few other small differences:

• The main chain of carbon atoms must contain both

carbons in the double bond. The main chain is

numbered so that the double bond gets the

smallest number.

• Before the root name, the number of the carbon

atom at which the double bond starts (the smaller

number) is written.

• If more than one double bond is present, the

prefixes di-, tri-, tetra-, etc. are used before the

-ene, and (strangely) the letter "a" is added after

the prefix for the number of carbon atoms.

A l k y n e n o m e n c l a t u r e

Hydorcarbons containing one or more triple bonds are

called Alkynes. Alkynes are named using the same general

procedure used for alkenes, replacing the suffix with -yne. If

a molecule contains both a double and a triple bond, the

carbon chain is numbered so that the first multiple bond gets

a lower number. If both bonds can be assigned the same

number, the double bond takes precedence. The molecule is

then named "n-ene-n-yne", with the double bond root name

preceding the triple bond root name (e.g. 2-hepten-4-yne).

Alkynes: Nomenclature

Although some common alkyne names, such as acetylene,

are still found in many textbooks, the International Union of

Pure and Applied Chemistry (IUPAC) nomenclature is

required for journal articles. The rules for alkynes in this

system are identical with those for alkenes, except for the

ending. The following rules summarize alkyne nomenclature.

1. Identify the longest continuous chain of carbon

atoms that contains the carbon-carbon triple bond.

The parent name of the alkyne comes from the

IUPAC name for the alkane of the same number of

carbon atoms, except the -ane ending is changed to

- yne to signify the presence of a triple bond. Thus, if

the longest continuous chain of carbon atoms

containing a triple bond has five atoms, the

compound is pentyne.

2. Number the carbon atoms of the longest continuous

chain, starting at the end closest to the triple bond.

Thus,

3. is numbered from right to left, placing the triple bond

between the second and third carbon atoms of the

chain. (Numbering the chain from left to right



incorrectly places the triple bond between the third

and fourth carbons of the chain.)

4. The position of the triple bond is indicated by placing

the lower of the pair of numbers assigned to the

triple-bonded carbon atoms in front of the name of

the alkyne. Thus the compound shown in rule 2 is 2-

pentyne.

5. The location and name of any substituent atom or

group is indicated. For example, the compound

6. is 5-chloro-2-hexyne.7. Nomenclature of Alkynes8. Alkynes are named similarly to alkenes. Much like

alkenes, you change the ending of the moleculename to designate a triple bond. Instead of the -aneor the -ene, you use -yne. You number the carbon tothe lowest possible carbon number.

9.10. The above molecule is called 2-pentyne.11. Alkynes have the lowest priority (other than alkanes,

which are THE lowest). This means that when youhave both a double bond and triple bond, thedouble bond gets the priority in numbering. Let'slook at this molecule:

12.13. This molecule is called 1-penten-4-yne.14.

15. The simplest possible alkyne is the two carbon triplebond, which would be called ethyne. However, inkeeping with "historical" names, the name"acetylene" is popular. This isn't anything that youcan deduce, it's one of the random names thatorganic chemists like to use. So, remember that thismolecule,

16.17. is called acetylene (although ethyne is still a good

name to use).18.

19. To name alkynes as substituent groups, such as thismolecule:

20.

21. First, count the longest parent chain. The longestparent chain is an octane. The substituent, locatedon carbon four, is an ethyne group. To namealkynes as substituents, you take the name, ethyne,and make it ethynyl. If the substituent was a threecarbon chain with a triple bond, it would be calledpropynyl.

ALCOHOLS

The following is list of some common primary alcoholsbased on the IUPAC naming system.

Name Molecular For

Methanol

(methyl alcohol)

CH3OH

Ethanol

(ethyl alcohol)

C2H5OH

Propanol C3H7OH

Butanol C4H9OH

Pentanol C5H11OH

Hexanol C6H13OH

Heptanol C7H15OH

Octanol C8H17OH



Rules for naming the alcohols

1. Find the longest chain containing the hydroxygroup (OH). If there is a chain with more carbonsthan the one containing the OH group it will benamed as a subsitutent.

2. Place the OH on the lowest possible number for

the chain. With the exception of carbonyl

groups

such as ketones and aldehydes, the alcohol or hydroxy groups gets first priority for naming.

3. When naming a cyclic structure the -OH isassumed to be on the first carbon unless thecarbonyl group is present, in which case the later will get priority at the first carbon.

4. When multiple -OH groups are on the cyclicstrucuture, number the carbons on which the -OH.

5. Remove e from the parent alkane chain and

add ol. When multiple alcohols are present use di,tri, etc before the ol but after the parent name. ex)2,3-hexandiol. IF the carbonyl group is presentthe -OH group is named as hydroxy, with thecarbonyl group chaning the parent chain name sothat it ends with al or one.

Ethane: CH3CH3 ----->Ethanol: (thealcohol found in beer, wine and other consumed sprits)

Secondary alcohol: 2-propanol

Other functional groups on an

alcohol: 3-bromo-2-pentanol

Cyclic alcohol (two -OH

groups): cyclohexan-1,4-

diol

Other functional group on the cyclic

structure: 3-hexeneol (the alkeneis in bold and indicated by numbering the carbonclosest to the alcohol)

A complex alcohol: 4-ethyl-3hexanol (the parent chain is in red and thesubstiuent is in blue)

Alkyl halides

IUPAC nomenclature of alkyl halides

12MAR

The IUPAC rules permit alkyl halides to be named in two

different ways, calledfunctional class

nomenclature and substitutive nomenclature. In

functional class nomenclature the alkyl group and the

halide (fluoride, chloride, bromide, or iodide) are

designated as separate words. The alkyl group is named on

the basis of its longest continuous chain beginning at the

carbon to which the halogen is attached.

Substitutive nomenclature of alkyl halides treats the

halogen as a halo-(fiuoro-, chloro-, bromo-, or iodo-)

substituent on an alkane chain. The carbon chain is

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numbered in the direction that gives the substituted carbon

the lower number.

When the carbon chain bears both a halogen and an alkyl

substituent, the two are considered of equal rank, and the

chain is numbered so as to give the lower number to

the substituent nearer the end of the chain.

IUPAC

Nomenclature Rules

Functional group suffix = halide (i.e. fluoride, chloride,

bromide, iodide)

Substituent name = halo- (i.e. fluoro, chloro, bromo, iodo)

Structural unit: haloalkanes contain R-X where X = F, Cl, Br,

I

Notes :

○ Haloalkanes can also be named as alkyl halides despite the

fact that the halogens are higher priority than alkanes.

○ The alkyl halide nomenclature is most common when the

alkyl group is simple.

Haloalkane style:

○ The root name is based on the longest chain containing the

halogen.

○ This root give the alkane part of the name.

○ The type of halogen defines the halo prefix, e.g. chloro-

○ The chain is numbered so as to give the halogen the lowest

possible number

Alkyl halide style:

○ The root name is based on the longest chain containing the

halogen.

○ This root give the alkyl part of the name.

○ The type of halogen defines the halide suffix, e.g. chloride

○ The chain is numbered so as to give the halogen the lowest

possible number.

Examples

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