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C h e m 1 B O r g a n i c C h e m i s t r y P a g e | 1

Organic Chemistry Ch. 21 Notes:

Homework: Read Chapter 21,

Chapter 21 problems: 35, 37, 43, 45, 53, 57, 59, 67, 73, 77, 91, 95, 99

Check MasteringChemistry homework

Organic Chemistry is the study of compounds containing the element carbon combined

with one of more other elements (H, O, N, S, P…).

Over 16 million carbon-containing compounds are known, and about 90% of the

newly synthesized compounds contain carbon. Although most organic compounds

contain only a few elements these compounds make up the majority of all known

substances naturally found and synthesized. Most common smells are caused by

organic molecules.

Functional groups identify organic molecules by their center of reactivity. By

understanding the functional group of organic molecules, you can predict how that

molecule reacts.

Solubility: Most organic compounds are nonpolar (the C-C and C-H bonds have low

electronegativity difference) so these compounds are soluble in nonpolar solvents


and not polar water. Some organic compounds have a polar area (C-O or C-N) and

if the molecule is small, will be soluble in water.

Most organics are neutral, the acidic organic compounds include carboxylic acids and

the basic organic compounds include amines.

Hydrocarbons are organic compounds containing only C and H and include alkanes,

alkenes, alkynes, and aromatics. These compounds are nonpolar. The

intermolecular attractions are London Dispersion Forces so the boiling points are

relatively low and increase as the molecular weight is increased. All hydrocarbons

undergo combustion reactions with oxygen in air.

Compounds: Organic compounds are easily decomposed into simpler substances by

heating, but inorganic substances are not. Inorganic compounds historically were


readily synthesized in the lab, but synthesis of organic compounds in the lab is

harder.

Carbon is unique: Carbon can bond to as many as four other atoms. Covalent bonds to

carbon are very strong and nonreactive. Carbon atoms can attach together in long

chains. Carbon atoms can attach together to form rings. Carbon atoms can form

single, double, or triple bonds.

Isomers: different molecules with the same molecular formula. Structural isomers

attach atoms in a different pattern. Stereoisomers have the same atom

attachments, but different spatial orientation; geometric stereoisomers are cis and

trans, while optical stereoisomers (also called enantiomers) have a chiral carbon-

attached to 4 different items and make nonsuperimposeable mirror images.

ALKANES: The general formula for an alkane is CnH2n+2

Alkanes contain only single bonds and are saturated hydrocarbons. Methane is the

simplest alkane containing only 1 carbon. CH4 has a tetrahedral structure with

angles of 109.5°. The term “normal” alkane represents that the carbons are all in a

row, the first carbon is attached to the second and so on without branching in

various directions. The common reaction with alkanes is combustion with oxygen.

The first 10 normal alkanes:

Name Molecular formula drawing (stick)

1 methane CH4

2 ethane

3 propane # isomers

4 butane 2

5 pentane 3

6 hexane 5

7 heptane 9

8 octane 18

9 nonane 35

10 decane 75

Structural formulas can be written as two- dimensional Lewis Structure formula,

condensed structural formula, and as three- dimensional Valence Shell Electron

Pair Repulsion (VSEPR) structure using a cabon skeleton formula, ball and stick


model, or space filling model. In addition to normal alkanes, isomers are possible

for all alkanes with 4 or more carbons.

Example 1: Draw and name 9 possible structural isomers of C7H16 as Lewis structures.

Alkanes can branch off.

a carbon is attached to one other carbon.

a carbon is attached to two other carbons.

a carbon is attached to three other carbons.

a carbon is attached to four other carbons.

CYCLOALKANES are alkanes that join the carbon chain together in a ring structure,

(CnH2n). The smallest cycloalkane has 3 carbons and is called cyclopropane

This structure may be drawn as a triangle in a condensed form where each point

represents a carbon with the appropriate number of hydrogen atoms.

Cycloalkanes with less than 5 carbons in a ring are strained since the angles are

less than the ideal 109.5°.


The most common and stable one is cyclohexane, C6H12, which can flex into chair

and boat configurations that keep angles at 109.5°

The most important chemical property of alkanes is combustion in oxygen to

produce heat, carbon dioxide, and water. Apart from the above reaction alkanes

are chemically inert.

ALKENES (also known as olefins) The general formula for an alkene is CnH2n

These unsaturated compounds contain a C=C double bond.

The simplest alkene, called ethene or more commonly ethylene, contains 2

carbons, (C2H4). Ethylene is a plant hormone and is important in the ripening

process of fruit.

Alkenes may have cis and trans isomers.

Example 2: Draw the cis and trans isomers of 2-butene…

cis-2-butene trans-2-butene

Example 3: Name the two structures below.

Alkenes undergo Addition Reactions.

Markovnikov's rule applies to reactions when there are two possible products.

This rule states that “the rich get richer”… carbon with more H preferably take an

additional H.

Example 4:

Finish the reactions indicating the preferred product


a) addition with H2

CH2=CH2 + H2 __Pt, Pd or Ni 500°C

b) addition with Cl2 or Br2 (the Br2 addition tests for unsaturation)

CH2=CH2 + Br2

c) addition with HX where X is a halogen

preferred

What is the other possible product, explain why it is less likely?

d) addition with H2O

CH2=CH-CH3 + H2O _H2

SO4

ALKYNES The general formula for an alkyne is CnH2n-2

These unsaturated hydrocarbons have a C≡C triple bond.

The simplest alkyne contains 2 carbons and is called ethyne or more commonly

acetylene. C2H2.

Alkynes also undergo addition reactions though less readily. Since the product still

has a double bond, it is often possible to get a second addition reaction.

Example 5: Draw the addition reaction of C2H2 with HCl.

AROMATIC HYDROCARBONS

In an aromatic hydrocarbon, 6 carbon atoms are connected in a planar ring

structure, joined by 6 sigma and 3 pi bonds (resonance) between carbon atoms.

Benzene (C6H6) is the simplest aromatic hydrocarbon.


Aromatic hydrocarbons undergo Substitution Reactions.

When two groups are attached on a benzene ring three isomers are possible.

ortho meta para

Example 6:

a) Draw and name the three isomers of the benzene ring in which two hydrogen

atoms have been replaced by chlorine atoms.

b) Draw the aromatic substitution reaction whose reactants are benzene (C6H6)

and nitric acid (HNO3) the catalyst is sulfuric acid (H2SO4) and the products

are nitrobenzene (C6H5NO2) and water (H2O)

c) Draw the substitution reactions on benzene with Br2. (halogenation )

FUNCTIONAL GROUPS:

• Other organic compounds are hydrocarbons in which functional groups have been

substituted for hydrogens


• A functional group is a group of atoms that show a characteristic influence on the

properties of the molecule, generally, the reactions that a compound will perform

are determined by what functional groups it has.

• Because the kind of hydrocarbon chain is irrelevant to the reactions, it may be

indicated by the general symbol R.

ALCOHOLS The general formula for an alcohol is R-OH

R represents any alkyl group (CxHy). The simplest alcohol

contains 1 carbon and is called methanol

Alcohols are neutral compounds. Small alcohols are soluble in water. They have

relatively high boiling points when compared to alkanes or ethers. Ethanol is an

important alcohol used in drinks and as an antiseptic.

PHENOLS For a phenol, R-OH ,the R is an aryl group (based on a benzene ring,

C6H5OH).

The simplest phenol is phenol (C6H5OH) where the group name comes from.

ETHER The general formula for an ether is R-O-R

The R and R' may be the same or different. The simplest ether is dimethyl ether

For complicated ethers with more than one functional group we use the general

name alkoxy, where alkoxy may be methoxy if there is 1 carbon, ethoxy if it has

two carbons, etc.

Ethers, like alkanes are virtually inert. This property makes them valuable as

solvents.

Two important chemical properties of ethers that laboratory workers must be aware

of are 1) highly volatile and 2) highly flammable

THIOLS, THIOETHERS

The general formula for a thiol (mercapton) is R–S–H. The general formula for a

thioether (sulfide) is R – S– R . In these compounds the oxygen in alcohols and

ethers is replaced with a sulfur. Thiols smell like rotten eggs.

ALDEHYDES and KETONES

The general formula for an aldehyde is R – CO–H. The simplest aldehyde is

called formaldehyde

The general formula for an ketone is R – CO–R. The simplest ketone is called


Propanone which is commonly called acetone.

Aldehydes may be prepared by the oxidation of primary alcohols

Ketones may be prepared by the oxidation of secondary alcohols.

Reduction (addition of H2) of aldehydes and ketones make primary and secondary

alcohols in that order.

Aldehydes are easily oxidized even under mild conditions. Ketones resist

oxidation. This fact allows simple tests to tell these compounds apart.

Aldehyde odors and flavors: Ketone odors and flavors:

butanal = butter acetophenone = pistachio

vanillin = vanilla carvone = spearmint

benzaldehyde = almonds ionone = raspberries

cinnamaldehyde=cinnamon muscone = musk

Carbonyl group C=O

The carbonyl group may undergo addition reactions. Unlike the C=C double bond

the C=O double bond is polar. Indicate the positive and negative ends of C=O and

H-CN.

C h e m 1 B O r g a n i c C h e m i s t r y P a g e | 1 0

CARBOXYLIC ACIDS and ESTERS

Carboxylic acids are sour tasting weak acids. The general formula for a carboxylic

acid is R – COOH. The simplest carboxylic acid is called

methanoic acid or formic acid

Esters have a sweet odor. The general formula for a carboxylic ester is R – COOR.

The simplest carboxylic ester is called methyl formate

It is useful to think of a carboxylic ester as being derived from a carboxylic acid

part R-CO(OH) and an alcohol part (H)-O-R', as in the synthesis of aspirin…

In naming carboxylic esters, do not try to name the ester as a whole. Name the

root carboxylic acid and change the suffix "ic acid" to "ate". For example acetic

acid becomes acetate. The first word is the name of the R' group in alcohol part.

Example 7: Name CH3-C-O-CH2CH3

||

O

AMINES

Amines smell bad. They form when proteins decompose. They are organic bases.

Many amines are biologically active (dopamine, epinephrine)

The general formula for an amine is R-NH2

The simplest amine is called methylamine


AMIDES

The general formula for an amide is R-CO-NH2

The simplest amide is called formamide

POLYMERS:

Polymers are very large molecules (macromolecules) made by repeated linking

together of small molecules (monomers)

Natural polymers are found in both the living and nonliving environment.

Synthetic polymers are polymers made in a lab from one, two, or three small

molecules linked in a repeating pattern (plastics, fabrics, adhesives)

Composites are materials made of polymers mixed with various additives such as

graphite, glass, metallic flakes

Polymerization is the process of linking the monomer units together

addition polymerization of vinyl chloride (CHCl=CH2) PVC= polyvinylchloride

condensation polymerization

Example 8:

Identify the functional groups in caffeine.


Chirality in Organic Chemistry

A molecule possessing a nonsuperimposeable mirror image is CHIRAL. These

compounds must have 4 different attached groups to a carbon (chiral center).

R (right-handed) and S (left handed) labels distinguish the two forms we call

enantiomers.

Enantiomers have identical physical properties and identical chemical behaviors in

nonchiral environments.

Racemic mixtures have equal amounts of both R and S enantiomers in a mixture.

Many drugs have only one effective enantiomer and the other is inert, an example

is R-Albuterol useful as a bronchodilator for asthmatics, the L Albuterol is not

effective.

Biochemistry Biochemistry is the chemistry of living organisms.

Amino Acids, the building blocks of proteins, have an amine and a carboxylic acid.

22 amino acids are found in nature and 20 are involved in making the proteins in

our body.


Organic Nomenclature Rules:

Saturated hydrocarbons - Alkanes: (CnH2n+2)

1) Find the longest continuous carbon chain and assign the parent name (1=methane, 2=ethane,

3=propane, 4=butane, 5=pentane, 6=hexane, 7=heptane, 8=octane, 9= nonane, 10= decane,

12=dodecane) i.e. if the longest chain is 5 carbons the end of the word will be pentane

2) Find groups not part of a chain and name as prefixed i.e. CH3 is methyl

3) Assign numbers to the carbons in the longest chain so attached groups have the lowest possible

numbers i.e. if the choice is 2 or 4 choose 2

4) If 2 or more identical groups are on one compound use prefixes but remember to give a carbon

chain number for each group; 2=di, 3=tri, 4=tetra, 5= penta, 6= hexa etc.

5) If 2 or more different groups are in the compound alphabetize i.e. chloro before fluoro and for

carbon groups: ethyl before methyl

6) Halogens go by F = fluoro, Cl = chloro, Br = bromo, I = iodo

7) For cycloalkanes, (CnH2n) begin counting carbons at any position and proceed in either

direction but you must end up with the lowest possible numbers. If only one substituent is

connected in a cycloalkane there is no need to number the carbon 1

8) Also, for cycloalkanes there is a possible for stereoisomers since the ring structure will not

permit free rotation. Stereoisomers may be labeled cis- for 2 groups on the same side and

trans- for 2 groups on the opposite side.

Unsaturated hydrocarbons - alkenes (CnH2n) and alkynes (CnH2n-2):

1) The suffix ene is used to represent a double bond between carbons the simplest is H2C=CH2

called ethene or more commonly ethylene (use the same prefixes as in the alkanes just change

ane to ene.

2) The suffix yne is used to represent a triple bond between carbons the simplest is HC=CH called

ethyne or more commonly acetylene

3) When the parent chain has more than 3 carbons a number position must identify where the

double or triple bond is located using the lowest possible number i.e. if a double bond in a 5

carbon chain is located between the 2nd and 3rd carbon it is called 2-pentene

4) Branches and halogen substituents are names as in rules for alkanes

5) the longest continuous carbon chain must include the double or triple bonded carbons even

though it may not be the longest chain. i.e. try to draw the structure for 2-methyl-1-butene

6) for cyclic compounds the double or triple bond will always be between carbon 1 and carbon 2.

try drawing 4-bromo-2,3-dimethylcyclohexene

7) Compounds with 2 or more double bonds have prefixed suffixes; i.e. 2 double bonds will be -

diene, 3 = triene. Try to draw 2-methyl-4-ethyl-1,3-heptadiene.

8) Since the C=C double bond cannot freely rotate one may get stereoisomers (this will not

happen in triple bonds) indicate cis- (H on same side) or trans- (H on opposite side) just before

the number position of the double bond if it is a geometric isomer. Try to draw cis-2 hexene

and trans-2-hexene.

Aromatic hydrocarbons - not unsaturated but has double bonds (includes a benzene ring) 1) The simplest is benzene (C6H6) which is a six carbon ring where every other C-C bond may

be written as a double bond in resonance. In reality the pi bonding is equally shared among all

carbons which makes a very stable compound not willing to undergo addition reaction.

Aromatic carbons undergo substitution reactions.


2) If only 1 group is attached no carbon numbers are needed

3) if 2 groups are attached the following rules apply

a) if the groups are on neighboring carbons o- is used for ortho-, or may use the

numbers1,2-

b) m- is used for meta-, or use the numbers 1,3-

c) p- is used for para-, or use the numbers 1,4-

4) If more than 2 groups just use the numbers that give the lowest sum.

Alcohols and Phenols: (R-OH) For common names give the name of the alkyl group followed by the word alcohol i.e. methyl

alcohol = CH3OH

For IUPAC naming use the following rules:

1) The longest chain must include the carbon bearing the OH group

2) the suffix ol represents the OH group and the lowest possible number is assigned to this carbon.

Try to draw 2-butanol

3) Alcohols may be classified as primary, secondary, or tertiary alcohols depending on how many

other C atoms are attached to the same carbon that the OH group is attached to. This

classification is important in reactions.

4) Phenols are aromatic compounds (benzene ring) which have a OH group

5) In complex compounds that have other suffixes hydroxy is used to indicate the OH group

Ethers: (R-O-R') 1) Give names of the R (organic) groups and add the word ether, i.e. ethyl methyl ether

2) If groups are the same use di ether, i.e. diethyl ether (some people omit the di)

3) For more complicated ethers use the alkyl group name followed by oxy then the other group.

Try to draw 2-methoxycyclopentanol

4) Cyclic ethers do not have ether in there names and follow rule 3.

Thiols (R-SH) and Thioethers (R-S-R) 1) These are analogous to the alcohols and ethers but S replaces the O. Naming is analogous but

use the term thiol not ol or alcohol and thioether not ether

(C=O is a carbonyl group that is found in aldehydes, ketones, carboxylic acids, carboxylic esters,

and amides)

Aldehydes (R-CH=O) and Ketones (R-COR')

1) Same rules as apply for others above

2) suffix = al for aldehydes, Carbon number is ALWAYS 1 for the aldehyde carbon. if an alcohol

of ether is also part of the compound then use hydroxy for the OH group and oxy for the ether.

3) suffix = one for ketones

4) If there is both a alkene or alkyne and a aldehyde or ketone both suffixes may be used. i.e. try

to draw 1-chloro-4-penten-2-one where a chlorine atom is attached to the 1st carbon the double

bond is between carbons 4 and 5 and the carbonyl (C=O) group is on the 2nd carbon.

Carboxylic acids (R-COOH):


1) Suffix oic acid other rules above are the same

2) the COOH carbon is always carbon number 1

3) The above IUPAC systematic naming is commonly used only for complicated compounds

normally the common names are used

examples:

H-COOH Formic acid (Latin word for ant (formica) since 1st isolated from red ants)

CH3COOH acetic acid

CH3CH2COOH propionic acid

CH3CH2CH2COOH butyric acid

CH3(CH2)3COOH valeric acid

CH3(CH2)16COOH stearic acid

HOOC-COOH oxalic acid

C6H5-COOH benzoic acid

Carboxylic Esters (RCOOR'): 1) The first word comes from the Alcohol part of the word (The R' which is connected to by a

single bond to an oxygen.) Name it as the alkyl group i.e. methyl

2) The second word is from the carboxylic part of the word ( the R which has the C=O carbonyl

group) the "ic acid" in the common form becomes ate.

acetic acid ==> acetate. Try to draw the structure methyl acetate.

Amines (R-NH2, R-NHR', or NR3):

1) Add the suffix amine to the alkyl group i.e. CH3NH2 = methylamine

2) The simplest aromatic one is aniline C6H5NH2

3) For secondary and tertiary amines place all the R group names before the suffix amine and use

di and tri as necessary.

4) When 1 R group is aromatic the amine is replaced with aniline

5) In complex compounds with competing suffixes the NH2 group is called "amino".

Amides (R-CO-NH2, R-CO-NHR', R-CO-NR'2): (CO is a C=O)

made by the dehydration of an amine and carboxylic acid

Amides are named after there corresponding carboxylic acids; "ic acid" amide, i.e.

CH3CO-NH2 is acetamide


Practice Problems: 1. A primary carbon is bonded directly to:

(a) 1 hydrogen (b) 1 carbon (c) 2 carbons (d) 3 carbons (e) 2 hydrogens 2. What functional groups are present in the following?

CH3-C-CH2-CH-CH=CH-CH3 ?

ll l O OH (a) ketone, alkene, alcohol (b) carboxylic ester, alkene, alcohol (c) aldehyde, alcohol, amine (d) phenol, carboxylic acid, alkene (e) amide, ether, thiol 3. What is the geometry of propane?

a) Planar with bond angles of 120°. b) Three-dimensional with bond angles of 90°. c) Three-dimensional with bond angles of 109.5°. d) Three-dimensional with bond angles of 120°. e) Three-dimensional with bond angles of 180°. 4. Why is the following name incorrect? 4-ethyl-5-methylcyclohexane

a) It is not named with the lowest possible numbers. b) Cycloalkanes do not contain alkyl groups attached to the ring. c) Ethyl and methyl groups are not found adjacent to one another on a ring. d) There is no such compound 5. How many hydrogen atoms are there in 1-chloro-2 methylbenzene

a) 3 b) 4 c) 5 d) 6 e) 7 f) 8 g) 9

6. Alkenes may have cis and trans isomers. Draw and identify the cis and trans isomers of 3-heptene 7. How can one test for saturation or unsaturation of hydrocarbons, include observations

one would see?

8. When is Markovnikov's rule needed and what does is say?

9. Draw and name all possible structural isomers with the formula C6H14

10. Reactions:


Finish and balance the following reactions, classify type of reaction as Addition, Substitution, or Combustion, and if 2 possible products are formed indicate the preferred product.

a)

+ HNO3

H+

Type b) CH2=CH2 + Br2 >

Type

c) C3H8 + O2 ____>

Type

d) CH3_CH=CH2 + H2O __H

2SO

4__>

Type 11. Draw the Structures: If you skip the Hydrogens at least put a line to indicate where H belongs and how many. (a) m-dichlorobenzene or 1,3 - dichlorobenzene (b) 2,2,3,3-tetrabromo-4-methyl-1-octanol (c) methyl acetate (d) 3-ethyl-3,4,6-trimethyl-2-decanone 12. Name the Structures: (a) C l O-H CH3 l | |

C H C C CH- C H 2 -C H 3

| l l l CH3 C l CH3 C H2 - C H 2 - C H 3

(b) CH3-O-CH2-CH3

(c) H-C-CH2-CH-CH2-CH3

ll l O CH3 (d) C H 3 - C - N H 2

ll


O 8. Circle and identify all the functional groups in the structural formula for the low-calorie sweetener aspartame below. List the functional groups here. For easier identification, number each circled group

9. Name the Structures: a) C H 3 - O - C H 3

b) O

|| C H 3 - C - O -C H 3

10. Draw and name all of the structural isomers with the formula C6H14 .

Reactions: Finish the following reactions and classify type of reaction as Addition, Substitution or Combustion. 11. a)

+ HNO3

H+

Type

b) CH3- CH2-C-H + H2 __Ni__>

ll O Type

12. Draw the Structures: (a) 2-chloro-3-hydroxy-4-methyl octanal (b) ortho-dichlorobenze (c) 3-ethyl-2- hexanone

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