Chem 109 Chapter 5

Front 1

What do alcohols, phenols, and ethers contain?

Back 1

Alcohols contain an –OH group attached to a saturated (sp3) carbon atom.
Phenols contain an –OH group attached to one of the carbons of a benzene ring (sp2).
Ethers contain an –O- atom bonded to two carbon atoms which can be either aliphatic or aromatic.

Front 2

Show me the formula make ups of ether, phenols, & alcohols?

Back 2

Front 3

Alcohols , phenols and ethers can be though of as what?

Back 3

Alcohols, phenols, and ethers can be thought of as organic derivatives of water:

Front 4

Explain hybridization of alcohols, phenols, & ethers?

Back 4

The oxygen atom in alcohols, phenols, and ethers is sp3 hybridized. Two of the sp3 orbitals are involved in bonding to hydrogen or carbon, and the remaining two contain lone-pair, or non-bonding, electrons.

Front 5

What are the bond angles and corresponding bond angles of H-O-C and in alcohols, phenols, and ethers?

Back 5

In water, the H-O-C bond angle is 104.5° due to repulsion of the bonding electron pairs by the larger non-bonding electron pairs.
In alcohols, phenols, and ethers the corresponding bond angles are closer to the expected tetrahedral 109.5° due to the replacement of one or both hydrogen atoms by larger carbon atoms.

Front 6

Constitutional isomerism in alcohols can arise from?

Back 6

Constitutional isomerism in alcohols can arise from:
Different carbon skeletons
Different placement of the –OH group on a carbon skeleton

Front 7

Which alcohols have no isomers?

Back 7

No isomers are possible for the simplest alcohols: methanol, CH3OH, and ethanol, CH3CH2OH.

Front 8

What are the 2 isomers for C3H8O?

Back 8

Two isomers are possible for C3H8O:

Front 9

What are the two different carbon skeletons possible for C4H10O?

Back 9

For alcohols having the formula C4H10O, two different carbon skeletons are possible:

Front 10

Where can the -OH group be placed in the carbon skeleton?

Back 10

The –OH group can be placed in two unique positions on each carbon skeleton:

Front 11

Review the properties of alcohols.

Back 11

An alcohol can be viewed as an alkane, cycloalkane, or alkene having a single oxygen atom inserted between one of the carbon atoms and its attached hydrogen.
As a result, the molecular formula of an alcohol still indicates the presence of a ring or double bond:
If the C:H ratio is the same as for an alkane, CnH2n+2, there is no ring or double bond.
If the C:H ratio is the same as for a cycloalkane or alkene, CnH2n, then either a ring or double bond is present.

Front 12

What are alcohol primaries, secondary and tertiary?

Back 12

Alcohols are classified as primary (1°), secondary (2°), or tertiary (3°).

Front 13

What are the names of different alcohols?

Back 13

Simple alcohols are usually referred to by their common names which consist of the alkyl group name followed by a space and the word alcohol.

Front 14

What are some characteristics of alcohols?

Back 14

Alcohols are characterized by strong secondary attractive forces and are characterized by:
Much higher boiling and melting points than those of hydrocarbons
Solubility in water

Front 15

What are some of the physical properties of alcohol?

Back 15

The strong secondary forces between alcohol molecules arise from hydrogen bonding:

Hint 15

Although not shown in the above illustration, each alcohol molecule is hydrogen bonded to several neighboring alcohol molecules.
The high melting and boiling temperatures of alcohols compared to the corresponding hydrocarbons is a direct result of the strengths of hydrogen bonds compared to London forces.

Front 16

What are some of the properties of alcohols alkanes and ethers?

Back 16

Front 17

Alcohols containing 3 or fewer carbons are miscible in what?

Back 17

Diols and triols have especially high boiling points compared to alkanes of similar size due to more extensive hydrogen bonding.
HOCH2CH2OH BP 198°C
CH3CH2CH2OH BP 97°C

Alcohols containing 3 or fewer carbons are completely miscible in water:

Hint 17

Alcohols containing 4 carbons are moderately soluble, 5 carbons slightly soluble, and more than 5 carbons are negligibly soluble.
An alcohol containing 5 or more carbons is soluble only if it contains two or more alcoholic groups.

Front 18

What can alcohol accept protons as a base from?

Back 18

An alcohol can accept a proton (act as a base) from strong acids such as sulfuric acid (H2SO4):

Hint 18

The equilibrium lies far to the left: only about 0.1% of the alcohol molecules become protonated, however, this small concentration is important in the dehydration reactions of alcohols.

Front 19

Describe the acidity of alcohols?

Back 19

The acidity of alcohols is too weak to be observed in reactions with NaOH or most other strong bases.
The acidity of alcohols is sufficient, however, to allow them to slowly react with active metals such as sodium to yield hydrogen gas:

Front 20

Summarize the dehydration of alcohol to alkenes?

Back 20

Alcohols can be dehydrated when heated with catalytic amounts of a strong acid. The reaction is called an intramolecular dehydration. An H­atom is lost from one carbon and an –OH group from an adjacent carbon:

Front 21

The dehydration of alcohols is the reverse of what?

Back 21

The dehydration of alcohols is the reverse of the hydration of alkenes.
LeChatelier’s principle allows the equilibrium position to be adjusted in favor of excess alcohol or excess alkene:
When hydration is desired, a large excess of water is used.
When dehydration is desired, the reaction is run at a temperature above the boiling point of the alkene formed, which distills out of the reaction mixture.

Front 22

Summarize the complicated course of secondary and tertiary alcohols?

Back 22

Dehydration of secondary and tertiary alcohols may follow a more complicated course than that for primary alcohols.
If the alcohol is asymmetric, two different products can be formed:

Hint 22

In this case, 2-butene is the major product.

Front 23

The more stable the alkene, the higher its yield in what?

Back 23

The more stable the alkene, the higher its yield in a dehydration reaction:

Front 24

The products from the oxidation of alcohols depend upon reaction conditions of what?

Back 24

The products from the oxidation of alcohols depend upon reaction conditions:
Combustion: All carbon atoms are oxidized to their highest oxidation state (CO2).
Selective (mild) oxidation: Only the carbon atom holding the –OH group is oxidized.

Front 25

Summarize oxidation of alcohols?

Back 25

The weakest bonds in an alcohol are the O-H bond and the adjacent C-H bond. These bonds only are oxidized during selective oxidations.
Typical selective oxidizing agents are MnO4- and Cr2O7-.
Primary, secondary, and tertiary alcohols respond differently to selective oxidation:

Front 26

Summarize the oxidation of primary alcohols?

Back 26

Primary alcohols are oxidized in two stages:
Stage 1: Simultaneous loss of hydrogens (dehydrogenation) from the –OH group and the adjacent C-H carbon producing a carbonyl group and a resulting compound called an aldehyde.
Stage 2: Oxidation of the –H attached to the carbonyl group of the aldehyde to –OH, producing a carboxylic acid.

Front 27

Summarize the oxidation of secondary alcohols?

Back 27

The reaction does not stop at the aldehyde when permanganate or dichromate are used as the oxidizing agent. Aldehydes can be produced using milder oxidizing agents.
Secondary alcohols: Oxidation cannot proceed beyond the carbonyl stage. These alcohols are oxidized to ketones.

Front 28

When does selective oxidation of alcohol occur in living systems?

Back 28

Selective oxidations of alcohols occur in living systems:
L-malate to oxaloacetate in the citric acid cycle.
Isocitric acid to -ketoglutarate in the citric acid cycle.
Ethanol to acetaldehyde by alcohol dehydrogenase.

Front 29

Permanganate and dichromate can be used for simple chemical diagnostic tests for what ?

Back 29

Permanganate and dichromate can be used for simple chemical diagnostic tests for primary and secondary alcohols.
Permanganate oxidation: MnO4- (purple solution) is converted into MnO2 (brown precipitate)
Dichromate oxidation: Cr2O72- (orange solution) is converted into Cr3+ (green solution)

Front 30

Permanganate and dichromate can be used for simple chemical diagnostic tests for primary and secondary alcohols. But what are its
Uses and limitations?

Back 30

Uses and limitations:
Primary and secondary alcohols are distinguished from tertiary alcohols which are unaffected by permanganate and dichromate.
Primary and secondary alcohols are distinguished from alkanes, cycloalkanes, aromatics, and esters, which do not undergo permanganate or dichromate oxidations.
Positive permanganate or dichromate tests do not distinguish primary and secondary alcohols from alkenes, alkynes, and phenols, which are also oxidized by these reagents.

Front 31

Phenol reacts completely with strong what?

Back 31

Phenol reacts completely with strong base

Front 32

Summarize the acidity of phenols?

Back 32

The higher acidity of phenols compared to alcohols is due to the electron-withdrawing effect of the phenyl ring compared to the R group of an alcohol.

Hint 32

The negative charge on the oxygen atom is dispersed around the benzene ring rather than leaving it entirely on the oxygen, as in the alcohol system. This effect is called charge dispersal.

Front 33

Phenols do not undergo dehydration, because of what?

Back 33

Phenols do not undergo dehydration, because that would form a triple bond within the benzene ring destroying its aromatic nature.
The oxidation of phenols is the basis of many antioxidants, both in physiological systems and in commercial products.

Front 34

Please summarize ethers?

Back 34

Ethers contain an oxygen atom bonded to two different carbon atoms. The carbon atoms can be either aliphatic or aromatic carbons.
The common nomenclature system uses the names of the groups attached to oxygen, in alphabetical order, followed by the word ether.
For ethers containing other than simple groups, the IUPAC system is used. In this case the ether is named as a member of some other family, with the more complex group determining the base name. The simpler group and the ether oxygen to which it is attached are treated as an alkoxy (RO) or aryloxy(ArO) group.

Front 35

Back 35

Front 36

What are some common names for cyclic ethers?

Back 36

Front 37

Any ether is a constitutional isomer of an alcohol containing the same number of what atoms?

Back 37

Any ether is a constitutional isomer of an alcohol containing the same number of carbon atoms. For instance, C2H6O:

Front 38

Summarize the properties of ether?

Back 38

The boiling point of dimethyl ether is higher than that of the corresponding alkane, propane, because the C-O-C bond is bent and the two carbon-oxygen bonds are polar.
This effect falls off rapidly with increasing alkane chain length. Diethyl ether has the same boiling point as its corresponding alkane, pentane.
Ethers as a class have much lower boiling points than alcohols due to the lack of hydrogen bonding between molecules.
Ethers are unreactive towards acids, bases, and oxidizing agents and are often used as solvents to carry out chemical reactions involving these substances.
Ethers, like alkanes, participate in combustion and halogenation reactions only.

Front 39

What are thiols?

Back 39

Thiols, or mercaptans, are the sulfur analogues of alcohols.
The –SH group is called the mercapto, or sulfhydryl, group.
The IUPAC nomenclature system adds the ending –thiol to the name of the alkane, but without dropping the final –e.
Thiols have distinct odors and flavors, often disagreeable (skunk).

Front 40

How do Thiols differ from alcohols?

Back 40

Thiols differ from alcohols:
• Thiols have considerably lower boiling points than those of alcohols, even though thiols have higher molecular masses, because thiols do not possess the strong hydrogen bonding of alcohols.

• Thiols are weak acids but much stronger than alcohols, because the S-H bond is weaker than the O-H bond, a consequence of the larger size of sulfur compared with oxygen. However, thiols are weaker acids than phenols.
• Thiols are easily oxidized to disulfides by many oxidizing agents:

Hint 40

Disulfides are named by naming the R groups attached to the sulfur
atoms followed by the word disulfide.

Front 41

Disulfides are easily reduced back to thiols by many reducing agents: Explain?

Back 41

In the preceding equations, the abbreviations (O) and (H) indicate
general conditions for selective oxidation and reduction, respectively,
without specification of the exact oxidizing or reducing agent.

Front 42

Disulfides are easily reduced back to thiols by many reducing agents: Explain?

Back 42

In the preceding equations, the abbreviations (O) and (H) indicate
general conditions for selective oxidation and reduction, respectively,
without specification of the exact oxidizing or reducing agent.

Front 43

• Thiols react with heavy metal ions such as lead (Pb2+) and
mercury(II) (Hg2+) to form what?

Back 43

• Thiols react with heavy metal ions such as lead (Pb2+) and
mercury(II) (Hg2+) to form insoluble salts:

Front 44

Summarize the Structural Relations of Alcohols, Phenols, and Ethers.

Back 44

Structural Relations of Alcohols, Phenols, and Ethers

• Alcohols contain an -OH (hydroxyl) group attached to a saturated (sp3) carbon.

• Phenols contain an -OH attached to one of the sp2-hybridized carbons of a benzene ring.

• Ethers, like alcohols and phenols, contain an oxygen that has bonds to two different atoms but, in contrast with alcohols and phenols, neither of the bonds is to hydrogen.

• The oxygen of an ether has single bonds to two different carbons.

Front 45

Summarize Constitutional Isomerism in Alcohols

Back 45

Constitutional Isomerism in Alcohols

• Constitutional isomerism in alcohols is due not only to different carbon skeletons but also to different placements of the -OH group within a carbon skeleton.

• The C:H ratio for an alcohol is the same as that for the corresponding hydrocarbon with the same number of double bonds and rings.

Front 46

Summarize Classifying and Naming Alcohols.

Back 46

Classifying and Naming Alcohols

• Alcohols are 1°, 2°, or 3° alcohols, depending on whether the carbon holding the -OH group is a 1°, 2°, or 3° carbon.

• In the IUPAC system, alcohols are named by using the longest continuous carbon chain containing the -OH group.

• The base name is preceded by a number indicating the position of the -OH group, and the ending of the name is changed from -e to -ol.

• Prefixes with numbers are then added at the front to indicate substituents attached to the longest chain.

• Common names for simple alcohols are formed by using the name of the alkyl group attached to the -OH group followed by the word alcohol.

Front 47

Summarize Physical Properties of Alcohols.

Back 47

Physical Properties of Alcohols

• Alcohols participate in hydrogen bonding, which results in high boiling and melting points and solubility in water.

Front 48

Summarize Acidity and Basicity of Alcohols.

Back 48

Acidity and Basicity of Alcohols

• Alcohols are very weak acids and bases.

Front 49

Summarize the Dehydration of Alcohols to Alkenes.

Back 49

Dehydration of Alcohols to Alkenes

• Intramolecular dehydration of an alcohol in the presence of an acid catalyst produces an alkene.

• When more than one alkene is possible, the major product is the most substituted alkene.

• A competing reaction for primary alcohols, but not secondary and tertiary alcohols, is intermolecular dehydration to an ether.

• At 180°C, the major product is alkene formed by intramolecular dehydration; at 140°C, the major product is ether formed by intermolecular dehydration.

Front 50

Summarize the Oxidation of Alcohols.

Back 50

Oxidation of Alcohols

• Primary and secondary alcohols undergo selective oxidation by permanganate (MnO4-) and dichromate (Cr2O72-) ions.

• Primary alcohols are oxidized to aldehydes, which are subsequently oxidized to carboxylic acids.

• Secondary alcohols are oxidized to ketones with no further oxidation possible.

• Tertiary alcohols are not oxidized.

• Permanganate and dichromate form the basis of simple chemical diagnostic tests for primary and secondary alcohols.

Front 51

Summarize Phenols.

Back 51

Phenols

• Substituted phenols are named by the IUPAC system as derivatives of the parent compound phenol.

• Phenols are more polar than alcohols and have higher boiling points and solubilities in water.

• Phenols are weak acids but much stronger than alcohols.

• Phenols undergo oxidation but not dehydration.

Front 52

Summarize Ethers.

Back 52

Ethers

• Ethers are isomeric with alcohols.

• The names of ethers containing simple groups consist of the names of the groups attached to the ether oxygen, followed by the word ether.

• Ethers have considerably lower boiling points than those of alcohols but are almost as soluble as alcohols in water.

• Ethers are unreactive toward acids, bases, and oxidizing agents.

Front 53

Summarize Thiols.



• Thiols are stronger acids than alcohols (but weaker than phenols), form insoluble products with heavy metal ions, and are oxidized to disulfides.

• Disulfides can be reduced back to thiols.

Back 53

Thiols

• Thiols contain the -SH group.

• They have lower boiling points than those of alcohols.

• Thiols are stronger acids than alcohols (but weaker than phenols), form insoluble products with heavy metal ions, and are oxidized to disulfides.

• Disulfides can be reduced back to thiols.

Front 54

Summarize alcohol reactions.

Back 54

Front 55

Summarize alcohol reactions 2?

Back 55

Front 56

Summarize reactions 3?

Back 56