ORGANIC CHEMISTRY

1.1 Functional Groups

are used to identify compounds but also to explain properties like solubility, melting & boiling points, etc.

there are many different functional groups but they contain one of 3 main components

i.e.

Carbon-Carbon Bonds

C-C single bonds are strong covalent bonds and are not very reactive

C=C and CΞC are more reactive and their 2nd and 3rd bonds are more easily broken

this allows these parts of a compound to be the sites where reactions occur

Single Bonds Between C & more Electronegative Bonds

where there is an unequal attraction of the electrons the bond is polar e.g. between C and a more electronegative atom

the C atom becomes more +ve and the O,N or halogen atom is more –ve

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an increase in polarity increases intermolecular forces which in turn increases the melting & boiling points

O-H and N-H bonds form bonds with special properties and they can form H-bonds with other OH groups, they increase intermolecular attractions but also enables these molecules to dissolve in polar solutes & solvents

“like dissolves like”

Double Bonded Carbon & Oxygen

this double covalent bond has 4 electrons being shared with ALL 4 electrons being more strongly attracted to the O atom

this bond is very polar with an accompanying increase in melting & boiling points and increased solubility in polar solvents

1.2 Hydrocarbons

alkanes- single C-C bonds, if all C’s have H’s attached, molecules

are called saturated hydrocarbons alkenes- have one or more C=C double bonds alkynes- have one or more CΞC triple bonds

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alkenes & alkynes are called unsaturated hydrocarbons because they have fewer than the maximum possible number of H atoms

can form either a straight chain or a cyclic (ring) structure

hydrocarbons which are attached to the main structure are called alkyl groups and are named according to the number of carbons

a 4th group are the aromatic hydrocarbons which have a unique ring structure

simplest is benzene and all others are derivatives of benzene

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Note: When naming propyl & butyl groups we have to consider how these groups attach onto the parent chain

i.e. when an alkyl group has 3 or more C atoms the group can attach either at an end C atom or at a middle C atom (see Fig.4 & 5)

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Aromatic Hydrocarbons

benzene ring usually considered to be the parent chain and attached alkyl groups are the branches

if a methyl group is attached, the molecule is called methylbenzene and we don’t need to assign a number

when we have 2 or more alkyl groups attached we need to use numbers (again numbering so that we have the lowest numbers)

Note: a) also known as ortho- or o-diethylbenzene b) also known as meta- or m-diethylenebenzene c) also known as para- or p-diethylenebenzene

when an aromatic molecule is too difficult to name sometimes we would consider the benzene ring as the attached branch and not the parent molecule

when the benzene ring is the attached branch it is called a phenyl group

(see Fig. 9 on page 20)2-phenylbutane or s-butylbenzene

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Physical Properties of Hydrocarbons

essentially nonpolar because they are made of C & H, atoms with similar electronegativities

main intermolecular forces are Van der Waals forces (electrons of one molecule with the nucleus of another)

because these forces are weak, molecules are easily separable from one another

small molecules have fewer electrons and weaker Van der Waal forces and therefore have lower boiling & melting points when compared to larger molecules

due to low polarity hydrocarbons generally have low solubility in polar solvents, like water

however, they will be good solvents for other nonpolar molecules

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1.3 Reactions of Hydrocarbons

alkanes because of their C-C bonds are relatively unreactive due to their being difficult to break

they do participate in combustion reactions, making them useful as fuels

although C-C bonds are difficult to break, the hydrogen atoms can be substituted by halogens in substitution reactions i.e. with F2, Br2, or Cl2

the product is referred to as a halogenated alkane, which are referred to as an organic family called alkyl halides

as the reaction above proceeds the concentration of bromoethane increases and bromine will react again to form 1,2-dibromoethane

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Reactions of Alkenes & Alkynes

both exhibit greater reactivity than alkanes i.e. if reacted with Br2 the reaction will be fast and will occur at room temperature

both undergo a characteristic reaction called an addition reaction, where atoms are added to the molecule with no loss of H atoms

addition reactions can involve halogens, H, hydrogen halides,and water, given the right conditions

Examples:

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common prefixes for functional groups include;

when molecules consisting of 2 identical atoms (H2) are added to a double bond only 1 possible product is formed, i.e a H atom gets added to each side of the double bond

but when molecules of a non-identical atom is added, 2 different products may form e.g.

experiments have shown that only one main product is formed which leads us to Markovnikov’s Rule….”the rich get richer”

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(see sample problem on page 26)

Reactions of Aromatic Hydrocarbons

although aromatic hydrocarbons are unsaturated, they do not undergo addition reactions except under extreme conditions

they do undergo substitution reactions and in fact the H atoms are more easily replaced than in alkanes

the reactivity of aromatic hydrocarbons are in between the alkanes & alkenes

Examples:

in reaction (b) further reaction of bromobenzene with Br2 results in substitution of another Br, resulting in 3 possible isomers of dibromobenzene

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i.e.

relatively low reactivity of benzene indicates that benzene is fairly stable and that the bonds in benzene are different than in the double & triple bonds in alkenes & alkynes

in another substitution reaction, benzene reacts with nitric acid in the presence of sulphuric acid to form nitrobenzene

benzene can also react with alkyl halides (R-X) in the presence of an aluminum halide catalyst (AlX3) ; alkyl group attaches to the benzene displacing an H atom on the ring

these products can undergo further reactions where one can design and synthesize compounds where the desired groups are attached in specific positions on the ring

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(see sample problem on page 29)

1.4 Organic Halides

organic halides are hydrocarbons with attached halogen atoms

e.g. Freon (chlorofluorocarbons), Teflon (polytetrafluoroethene), etc.

Naming Organic Halides

consider the halogen atom as an attachment on the parent chain

halogen name is shortened to its root namei.e. Fl=fluoro-, Cl=chloro-, etc.

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Properties of Organic Halides

halogens are more electronegative so the organic halide molecules are more polar i.e. C-halogen bonds polarity > C-H bonds

therefore the intermolecular forces are stronger with halide containing molecules and they have higher boiling points and being more polar can dissolve in polar solvents

compounds may contain 1,2, or 3 halogens per molecule the more halogen atoms per molecule, the more polar the

molecule, the higher the boiling point etc.

Read the Cost of Air Conditioning on page 34.Preparing Organic Halides

can be produced by halogenation reactions

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similarly, if we wanted to produce a halide of a benzene ring, we would arrange a substitution reaction with a halogen

Preparing Alkenes from Alkyl Halides: Elimination Reactions

alkyl halides can eliminate a H atom and a halogen atom from adjacent C atoms resulting in the formation of a double bond and therefore an alkane in an elimination reaction

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1.5 Alcohols and Ethers

structurally similar except that alcohols have the general form R-O-H and ethers have the general form R-O-R, where R represents alkyl groups

properties are generally due to the polar OH groups and other non-polar groups

Alcohols

Naming Alcohols

IUPAC rules say that any R-OH should end with the suffix “–ol” which is added to the parent chain i.e. methane with an OH is called methanol

an alcohol with 2 carbons is called ethanol and so on….. when an alcohol has more than 2 C’s or OH groups we

number the C atoms to locate the OH groups the 2 isotopes of C3H7OH are;

2-propanol is also known as isopropanol, i-propanol or isopropyl

alcohol

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1°, 2° and 3° Alcohols

can also be classified by the type of C where the –OH is attached

since C can form 4 bonds, the C atom can be attached to 1, 2 or 3

alkyl groups resulting in 1°, 2° and 3° alcohols example 1-propanol is a primary alcohol, 2-propanol is a secondary alcohol, while 2-methyl-2-propanol is a tertiary alcohol

important for predicting reactions because the reactions are determined by the availability of H atoms or alkyl groups in key positions

Polyalcohols

alcohols containing more than 1 OH group are called polyalcohols

the suffixes –diol and –triol are added to the entire alkane name to indicate the number of OH groups

e.g. 1,2-ethanediol (ethylene glycol) found in antifreeze

the OH groups can also be considered as an added group to a

parent chain and has the prefix –hydroxy

i.e. 1,2,3-propanetriol is also called 1,2,3-trihydroxypropane

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Cyclic Alcohols

cyclic compounds with OH groups attached are called cyclic alcohols

many compounds are known by their common names which end in –ol i.e. menthol, cholesterol

aromatic compounds with attached OH groups compose the aromatic alcohol group

simplest in this group is hydroxybenzene or phenol phenol is a colourless solid, slightly soluble in water

(due to OH group), used in industrial preparation of plastics, drugs, dyes & weedkillers

when naming cyclic or aromatic alcohols the OH group may be considered as a group attached to the parent ring

i.e. phenol is also named hydroxybenzene a benzene ring with 2 adjacent OH groups would be

named 1,2-dihydroxybenzene

(see sample problems and examples on pages 40 & 41)

Properties of Alcohols

boiling points of alcohols are higher than those of their parent alkanes due to their OH groups which make them more polar and gives them the capability of forming H bonds

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simple alcohols are also more soluble in water for the same reason

in longer alcohols the hydrocarbon portion is nonpolar making them good solvents for nonpolar molecular compounds, as well

Reactions Involving Alcohols

a) Hydration Reactions

many alcohols are prepared by addition reactions of water to unsaturated hydrocarbons

this type of addition reaction is called a hydration reaction (using Markovnikov’s rule)

b) Combustion of Alcohols

c) Elimination Reactions

reverse of a hydration reaction under certain conditions alcohols decompose to produce

alkenes and water this reaction is catalyzed by concentrated sulphuric acid called a dehydration reaction

(see sample problems on pages 43 & 44)

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EthersProperties of Ethers

structure similar to water H-O-H and alcohols R-O-H only in ethers, structure is R-O-R (where R=alkyl groups)

alkyl groups may be identical or different there are no OH bonds in ethers so they do not form

hydrogen bonds C-O bonds are polar and the v-shape of the C-O-C group

make ether molecules more polar than hydrocarbons intermolecular attractions between ether molecules are

stronger than hydrocarbons but weaker than those in alcohols, which is seen in Table 2 by looking at the boiling points

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ethers are good solvents for organic reactions because they mix readily with both polar and non-polar substances

C-O bonds are polar so ethers can dissolve polar substances while their alkyl groups allow them to dissolve non-polar substances

C-O bonds are hard to break, making ethers unreactive another property of a good solvent

Naming Ethers

named by adding –oxy to the prefix of the smaller hydrocarbon group and joining it to the alkane name of the larger hydrocarbon group

example:CH3-O-C2H5 is methoxyethane NOT ethoxymethane

names are sometimes derived from the 2 alkyl groups followed be the word ether

example: methoxyethane would be methyl ethyl ether

when the 2 alkyl groups are the same di- is used i.e. ethoxyethane is diethyl ether

Preparing Ethers from Alcohols: Condensation Reactions

ethers are formed when 2 alcohols react eliminating a molecule of water

this type of reaction where water is released is called a condensation reaction

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(see sample problem on page 47)

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Aldehydes & Ketones

aldehydes and ketones are closely related in that they both contain a carbonyl group (C=O)

in ketones, the carbonyl group is attached to 2 alkyl groups and no H groups

in aldehydes, the carbonyl group is attached to at least 1 H atom and is also attached to either another H atom or an alkyl group

i.e. in ketones the C=O is in the middle and in aldehydes the C=O is at the end of the carbon chain

Naming Aldehydes & Ketones

aldehydes are named by taking the parent alkane name, dropping the e and adding the suffix -al

the simplest aldehydes is HCHO, has only 1 C and therefore the parent chain name is methane and as an aldehyde the name becomes methanal (formaldehyde)

2 carbon aldehyde would be named ethanal (acetaldehyde),etc.

ketones are named by replacing the e ending of the alkane with

-one the simplest ketone is propanone, CH3COCH3 (acetone)

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if a ketone has 5 or more carbons in the carbon chain containing the carbonyl group than we need to specify the location of the carbonyl group

Example: in 2-pentanone the carbonyl group is the second carbon in the chain

(see the sample problem on pages 50 & 51)

Properties of Aldehydes & Ketones

aldehydes & ketones have lower boiling point’s than analogous alcohols and are less soluble in water as they don’t have OH groups and don’t participate in H bonding

C=O is a strongly polar group so that they are both more soluble in water than are hydrocarbons

Are good solvents because they will mix with both polar and non-polar substances

Preparing Aldehydes and Ketones from Alcohols: Oxidation Reactions

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oxidation reaction in organic chemistry implies a gain of oxygen or a loss of hydrogen

in the following reactions oxygen is supplied by compounds called oxidizing agents like H2O2 (hydrogen peroxide), K2Cr2O7 (potassium dichromate) and KMnO4 (potassium permanganate)

the (O) removes 2 H atoms, one from the OH and the other from the “R” group resulting in the formation of a C=O group + an H2O

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From Aldehydes & Ketones to Alcohols: Hydrogenation Reactions

the carbonyl group can undergo an addition reaction with H but not other reactants

high heat, pressure and a catalyst are needed for this hydrogenation reaction

the reaction adds H to the C=O which results in an OH group which produces an alcohol

Note: due to the type of groups attached to the carbonyl C atom, aldehydes always produce primary alcohols while ketones always produce secondary alcohols

(see sample problems on pages 55 & 56)

Carboxylic Acids & Esters

organic acids have a carboxyl functional group –COOH and are called carboxylic acids

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like inorganic acids, carboxylic acids can react with OH containing compounds to form an organic “salt” called an ester

Carboxylic Acids

are generally weak acids, are found in citrus fruits, crab apples, rhubarb, and other foods known by their sour tangy taste

carboxylic acids also have distinct odours that can be used in law enforcement

Naming Carboxylic Acids

the carboxyl group -COOH combines the C=O and OH groups that we are familiar with already

IUPAC name is formed by taking the name of the alkane or alkene with the same number of C atoms as the longest chain in the acid

(don’t forget to include the C in the –COOH group) the ending –e in alkane or alkene is changed to –oic and

adding the word acid

Examples:

methane….methanoic acid (HCOOH)methanoic acid is commonly called formic acid ethane…ethanoic acid (CH3COOH) commonly called acetic acid (makes vinegar taste sour)

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simplest aromatic acid is phenylmethanoic acid (benzoic acid)

some acids contain multiple COOH groups i.e. oxalic acid

(2 COOH groups bonded to each other)

when naming acids with multiple COOH groups, use –dioic acid when COOH’s are at each end of the parent chaine.g HOOC-CH2-COOH is propanedioic acid

when more COOH groups are present the COOH groups can be named as groups on the parent chain and are not counted as part of the parent chain

(see sample problem on page 60)

Properties of Carboxylic Acids

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due to C=O and OH groups in carboxyl groups these molecules are polar and can form hydrogen bonds with each other and water molecules

smaller acids have similar solubility to alcohols but larger ones are relatively insoluble

carboxylic acids have the properties of acids and can react organic “bases” to form “salts”

due to intermolecular attractions between the carboxyl functional groups the melting points are higher than their corresponding hydrocarbons

Preparing Carboxylic Acids

when an alcohol is mildly oxidized an aldehyde is produced and further oxidation results in the formation of a carboxylic acidi.e.

(O) in these reactions is supplied by an oxidizing agent

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using an oxidizing agent that changes colour is that basis of the breathalyser test

(see sample problems on pages 62-63)

From Carboxylic Acids to Organic “Salts”: Esterification

carboxylic acids can react in neutralization reactions in reactions with alcohols (where the alcohol acts as an

organic base) this reaction forms an ester and water

Esters

responsible for the colours and odours of plants (table 2 p. 64&65)

generally have the structure of

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Naming and Preparing Esters

name has 2 parts first part from the alkyl group from the alcohol used and

the second part is from the acid the second part also changes its suffix from –oic to –oate

e.g.

the general formula can be written as RCOOR1

RCO from the carboxylic acid while the OR1 comes from the alcohol

i.e. for an ester the acid is the first part drawn but is the 2nd part of the name

(see sample problem on p. 65&66)Properties of Esters

compared to a carboxylic the functional group is similar but is missing the OH group

i.e. the –OH is replaced by an –OR group therefore esters are less polar, less soluble in water and

have lower melting and boiling points than their parent acids

acidity of carboxylic acids is from the H on the OH group, esters missing the OH group are not acidic

Reactions of Esters: Hydrolysis

when an ester is treated with an acid or base, it will split into its acid and alcohol components

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this type of reaction is called hydrolysis

saponification is a reaction where an ester is hydrolyzed basis of soap making where fats and oils (esters of long chain acids) are heated with a strong base which causes a hydrolysis reaction and the sodium salts of the acids are “soap”

Amines and Amides

these are compounds that contain nitrogen, as well as, carbon, hydrogen, oxygen, etc.

amines are like NH3 with 1,2, or 3 of its H’s replaced with alkyl groups and are classified as 1°, 2° or 3°

amines are organic bases and can react with carboxylic acids to form nitrogen-containing (nitrogenous) organic salts called “amides”

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amides have the functional group –CON, which can be found in proteins, etc.

Amines

when once living things break down to form amines which have an unpleasant odour e.g. smell of rotting fish due to a mixture of amines

decomposing animal tissue produce amines called putrescine and cadaverine

Naming Amines

can be named in 2 ways;1. as a nitrogen derivative of an alkane (IUPAC way)

e.g. CH3NH2 would be aminomethane or2. as an alkyl derivative of ammonia e.g.

methylamine

Examples:

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if there are 2 amino groups, they are called diamines so IUPAC name for cadaverine is 1,5-diaminopentane

a shortcut is to use N to show the substituted groups on the N atom of the amino group i.e see last 2 molecules above

an alternative naming system is where the name implies a derivative of ammonia

see 2° amine above, which has 2 alkyl groups on the N atom, a methyl and a butyl which is given the name butylmethylamine

see 3° amine above, which has 3 methyl groups around the central N atom, which is given the name trimetylamine

(see sample problems on page 71)

Properties of Amines

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amines have higher boiling points and melting points than hydrocarbons of the same size and smaller amines are soluble in water due to N-C and N-H both of which are polar

when N-H bonds are present, hydrogen bonding can occur with water which explains the high solubility of amines in water

N-H bonds are less polar than O-H so amines will boil at lower temperature

Preparing Amines

can be prepared by reaction of ammonia (a weak base) with an alkyl halide

this reaction if left to continue can produce a mixture of 1°, 2°, 3° amines i.e.

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these 3 components can be separated by fractional distillation due to their different boiling points

Amides

similar to esters but here we have a N atom replacing the O atom

the amide functional group consists of a carboxyl group attached to an N atom

Naming and Preparing Amides

carboxylic acids react with ammonia or with 1° and 2° amines (organic bases) to produce amides (organic salts)

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both of these reactions are condensation reactions and water is formed

again, the amide functional group is carbonyl group attached to a N atom

N makes 2 more bonds to either H atoms or alkyl groups

tertiary amines will not undergo the above reaction which needs a H atom on the amine

note the similarity between the synthesis of an ester and the synthesis of an amide from a primary amine below

naming amides is similar to naming esters esters end in –oate while amides end in –amide name of an amide is made up of 2 parts:

1. first part from the amine in the example above the amine is methylamine

so name begins with methyl 2. second part comes from the name of the acid in the example above butanoic acid…oic is

dropped and amide is added…butanamide the name therefore is methyl butanamide, as with esters

the name is separated into 2 words when there are 1 or more alkyl groups attached to the N

atom in the amide linkage we use the letter N to clarify the location of the group i.e.

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(see sample problem on page 75)

Properties of Amides

amides are weak bases, insoluble in water low molecular weight amides are slightly soluble in water

because of the hydrogen bonding taking place between the amides` polar N-H bonds and the water molecules

amides whose N atoms are bonded to 2 H atoms have higher melting and boiling points than amides that have more attached alkyl groups

explained by increased hydrogen bonding

Reactions of Amides

like esters, amides can be hydrolyzed in acidic or basic conditions to produce a carboxylic acid and an amine

reverse of formation reactions of amides

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(See sample problem on page 77)

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