The Rules for Boiling Points - PDF Free Download

The Rules for Boiling Points The boiling points of compounds depend on how strongly they stick together: The more strongly they stick together, the higher the boiling point (the more heat it takes to rip them apart). There are two main forces that hold molecules together: -Hydrogen bonds These require both positive hydrogens (from -H or N-H bonds) and electron lone pairs (found mainly on and N atoms) -London forces (see Chapter 6, pages 169-170) -Bigger molecules have stronger intermolecular forces, and higher boiling points, other things being equal. -These forces are very short-range, so this also depends on how close the molecules can get together. The more branches in an alkane, the harder it is for them to get close. Branched alkanes thus have lower densities and lower boiling points (see page 257). Copyright Houghton Mifflin Company. All rights reserved. 13 1

Recent News A recent report asserts that dogs have been trained to detect cancer by sniffing samples taken from the breaths of healthy persons and cancer victims. Dogs can detect odors at the low parts per billion (ppb) level. It is claimed that tumor cells emit different chemicals-- alkanes and benzene derivatives--than healthy cells. Reference: The New York Times, January 17, 2006, p. D5. Copyright Houghton Mifflin Company. All rights reserved. 13 2

ADVICE It is very important that you begin to study the material as early as possible. Working the practice problems and answering the practice questions is absolutely essential. Copyright Houghton Mifflin Company. All rights reserved. 13 3

Chapter Thirteen Hydrocarbon Derivatives II: Carbon xygen Double Bonds

13.1 The Carbonyl Group A Carbonyl Group consists of a carbon atom and an oxygen atom joined by a double bond. This is by definition a carbonyl group (C=). H 3 C CH 3» Acetone for example contains a carbonyl group. Pronounced carbon-eel Carbonyl groups are strongly polarized, with a partial positive charge on carbon and partial negative charge on oxygen. Copyright Houghton Mifflin Company. All rights reserved. 13 6

Because oxygen is more electronegative than carbon, it pulls the electrons in the double bond toward oxygen creating a partial negative charge on oxygen and a partial positive charge on the carbonyl carbon atom. Much of the reactivity of carbonyl groups results from this polarization. E.N. = 3.5 E.N. = 2.5 Copyright Houghton Mifflin Company. All rights reserved. 13 7

The polarity of the carbonyl group contributes to its reactivity. The carbonyl carbon is bonded to oxygen and two other atoms. The bond angles between the three components on carbon are 120 o or close to it. Carbonyl compounds are broadly divided into two groups: (1) aldehydes and ketones are in one group and (2) the second group contains carboxylic acids, esters, and amides. Copyright Houghton Mifflin Company. All rights reserved. 13 8

An aldehyde is a compound that has at least one hydrogen atom attached to the carbon atom of a carbonyl group. H CH 3 an aldehyde a ketone R H The R group in an aldehyde can be H, alkyl, or aryl. Copyright Houghton Mifflin Company. All rights reserved. 13 11

Some Common Aldehydes Formaldehyde, H(C=)H: Toxic but useful. It kills viruses, fungi, and bacteria. It is used in disinfecting and sterilizing equipment. Acetaldehyde CH 3 (C=)H: Sweet smelling and narcotic. Present in ripe fruits, especially in apples. It is less toxic than formaldehyde. Benzaldehyde Ph(C=)H: il of almonds; used to make dyes, perfumes, and specific flavors. Copyright Houghton Mifflin Company. All rights reserved. 13 12

Naming Aldehydes The simplest aldehydes are known by their common names, formaldehyde, acetaldehyde, benzaldehyde, and so on. To name aldehydes systematically in the IUPAC system, the final e of the name of the alkane is replaced by al. Copyright Houghton Mifflin Company. All rights reserved. 13 14

When a compound contains more than one type of functional group, the suffix for only one of them can be used as the ending of the name. The IUPAC rules define priorities that specify which suffix should be used: 1. Carboxylic acid 2. Aldehyde 3. Ketone 4. Alcohol 5. Amine 6. Alkene 7. alkyne Remember that alkoxy (ether), halogen (halide), and alkyl Groups are treated as substituents and listed in alphabetical order. Copyright Houghton Mifflin Company. All rights reserved. 13 15

1. To name an aldehyde, select the longest chain which contains the aldehyde functional group. 2. Then name the parent chain by changing the -e ending to -al. 3. Number the parent chain starting with 1 for the aldehyde carbon atom. 4. Determine the identity of the substituents, and add this information to the front of the parent chain name. H H pentane pentanal pentanal 3-hydroxypentanal Note that the aldehyde is the primary functional group and so this is named as an aldehyde and not as an alcohol. Copyright Houghton Mifflin Company. All rights reserved. 13 16

Properties of Aldehydes and Ketones The polarity of the carbonyl group makes aldehydes and ketones moderately polar compounds. As a result, they have boiling points higher than alkanes and are reactive. Aldehydes and ketones do not form hydrogen bonds to each other, however, they form hydrogen bonds with water using the lone pairs of electrons on oxygen. Aldehydes and ketones have boiling points intermediate between alkanes and alcohols of similar size. Copyright Houghton Mifflin Company. All rights reserved. 13 18

Rules for Solubility Like dissolves like. This means that polar compounds dissolve best in polar solvents (like water and alcohols) and nonpolar compounds dissolve best in nonploar solvents (like hexane and benzene). Some compounds, like alcohols, have a polar part (the -H group) and a nonpolar part (the hydrocarbon portion). Solubility in water depends on which part dominates. Alcohols with a large organic (hydrocarbons) portion are not very soluble in water. Carbonyl compounds will be soluble in water if their hydrocarbon portion is not too large. The water can form hydrogen bonds to the electron lone pairs on the oxygen. But if the organic portion is too large, solubility is decreased. Acetone, CH 3 -(C=)-CH 3, is an excellent solvent for both polar and nonpolar compounds. Copyright Houghton Mifflin Company. All rights reserved. 13 20

--Simple ketones are excellent solvents because they dissolve both polar and nonpolar compounds; acetone (CH 3 HC=) is an example. --The lower boiling aldehydes and ketones are flammable. --The simple ketones have low toxicity, however, many simple aldehydes are toxic because they react with proteins and other biomolecules; example -formaldehyde. Copyright Houghton Mifflin Company. All rights reserved. 13 21

xidation of Aldehydes Primary alcohols can be oxidized to aldehydes and secondary alcohols to ketones. Aldehydes can be further oxidized to carboxylic acids. Since ketones cannot be further oxidized, application with a mild oxidizing agent can be used as a test to distinguish between aldehydes and ketone. Copyright Houghton Mifflin Company. All rights reserved. 13 22

Primary alcohol: CH 3 CH 2 H + [] CH 3 CH= + H 2 CH 3 CH= + [] CH 3 CH + H 2 [oxidation to an aldehyde] [further oxidation to an organic acid] Secondary alcohol: H [oxidation to a ketone] CH 3 CH-CH 3 + [] CH 3 (C=)CH 3 + H 2 The ketone cannot be further oxidized. Copyright Houghton Mifflin Company. All rights reserved. 13 23

A positive Tollens test for aldehydes involves the formation of a silver mirror. (a) An aqueous solution of ethanal is added to a solution of silver nitrate in aqueous ammonia and stirred. (b) The solution darkens as ethanal is oxidized to ethanoic acid, and Ag +1 ion is reduced to silver. (c) The inside of the beaker becomes coated with metallic silver. The aldehyde is oxidized and the metal is reduced. Tollens test: Ag + (soluble) Ag metal (mirror). Copyright Houghton Mifflin Company. All rights reserved. 13 24

Benedict s solution, which is blue in color, turns brick red when an aldehyde reacts with it. The aldehyde is oxidized and the metal is reduced. Benedict s test: Cu ++ (blue) Cu + (brick red). Copyright Houghton Mifflin Company. All rights reserved. 13 25

Reduction of Aldehydes and Ketones Reduction is the reverse of the oxidation reaction. Reduction of a carbonyl group is the addition of hydrogens across the double bond to produce an H group. Aldehydes are reduced to primary alcohols, and ketones are reduced to secondary alcohols. Reduction of the carbonyl group occurs by formation of a bond to the carbonyl carbon by a hydride, H: -, ion accompanied by bonding of a H + ion to the carbonyl oxygen atom. Copyright Houghton Mifflin Company. All rights reserved. 13 26

Acetone, CH 3 (C=)CH 3 ): It is one of the most widely used solvents. It can dissolve most organic compounds and is also miscible with water. Acetone is highly volatile and is also highly flammable. Ketones, like aldehydes, occur widely in Nature. 2-heptanone cloves carvone spearmint flavoring Copyright Houghton Mifflin Company. All rights reserved. 13 28

Some ketones are best known by their common names which give the names of the two alkyl groups bonded to the carbonyl group followed by the word ketone. For example, ethyl methyl ketone = CH 3 -(C=)-CH 2 -CH 3 Ketones are named systematically (IUPAC) by replacing the final e of the corresponding alkane name with one. The numbering of the alkane chain begins at the end nearest to the carbonyl group. The location of the carbonyl group is indicated by placing the number of the carbonyl carbon in front of the name; e.g. 2- propanone = acetone. The above compound is 2-butanone Copyright Houghton Mifflin Company. All rights reserved. 13 29

The physical properties of ketones closely parallel the properties of aldehydes; i.e. their boiling points are intermediate between alkanes and alcohols. Ketones are not readily oxidized. Ketones are readily reduced to secondary alcohols. H 2 N i catalyst H Copyright Houghton Mifflin Company. All rights reserved. 13 31

Carboxylic Acids and Their Derivatives: Properties and Names Caboxylic acids have an H group bonded to a carbonyl group. In their derivatives, H is substituted by other groups. Such as, Esters have an R group bonded to a carbonyl group. Amides have an NH 2 group bonded to a carbonyl group. Copyright Houghton Mifflin Company. All rights reserved. 13 34

Carboxylic Acids are acidic Carboxylic acids donate a proton to bases. Carboxylic acids hydrogen bond with each other. As a result of hydrogen bonding, they have higher boiling points than similar alkanes. Copyright Houghton Mifflin Company. All rights reserved. 13 35

Two common NSAID s (non-steroidal anti-inflammatory drugs) are Ibuprofen (a.k.a. Motrin and Advil) and Naproxen (a.k.a. Naprosyn and Aleve). They are both carboxylic acids. C 2 H C 2 H ibuprofen naproxen Chronic long term used of these TC drugs has recently been shown to increase the risk of heart disease. Copyright Houghton Mifflin Company. All rights reserved. 13 37

--Carboxylic acids have a sharp and strong odor. --Up to four carbon containing carboxylic acids are water soluble. --Carboxylic acids are named systematically (IUPAC) by replacing the e at the end of the alkane name with oic acid. If alkyl or other substituents are present, the chain is numbered beginning at the CH end. Copyright Houghton Mifflin Company. All rights reserved. 13 39

H Carboxylic acids have a higher priority when naming. Therefore, this molecule is not named as a ketone, but instead is named as a carboxylic acid. 5-oxohexanoic acid H 2-ethyl-5-methylbenzoic acid Copyright Houghton Mifflin Company. All rights reserved. 13 40

Dicarboxylic acids, which contain two CH groups, include the biochemicals succinic acid, HC-CH 2 -CH 2 -CH, and glutaric acid, HC-CH 2 -CH 2 -CH 2 -CH. Unsaturated acids are named systematically in the IUPAC system with the ending enoic acid. Acids with larger saturated alkyl groups are waxy, odorless solids. Water solubility decreases as the size of the alkyl group increases. Copyright Houghton Mifflin Company. All rights reserved. 13 41

Notes on Some Common Carboxylic Acids Formic acid, HCH: Chemical that is present in the sting of ants. Acetic acid, CH 3 CH: dilute (5%) aqueous acetic acid is known as vinegar. Butyric acid, CH 3 CH 2 CH 2 CH: Chemical responsible for odor of rancid butter. Amino acids, the building blocks of proteins, have the general formula R-CH(NH 2 )-CH. Citric acid: Present in citrus fruits and blood. Copyright Houghton Mifflin Company. All rights reserved. 13 44

Acidity of Carboxylic Acids Carboxylic acids are weak acids. Acid strengths of common carboxylic acids are about the same as that for acetic acid. Carboxylic acids undergo neutralization reactions with bases and produce water and a carboxylic acid salt. The sodium and potassium salts of carboxylic acids are ionic solids that are more soluble in water than the carboxylic acids themselves. Copyright Houghton Mifflin Company. All rights reserved. 13 45

Carboxylic acids are acids because they donate a proton to a base; e.g. water. H + H H + H 3 + butyric acid carboxylate ion hydronium ion A carboxylate ion is a negative ion produced when a carboxylic acid loses a proton (acidic hydrogen atom). In this case the equilibrium lies far to the left because carboxylic acids are weak acids and therefore do not completely ionize. Copyright Houghton Mifflin Company. All rights reserved. 13 46

A given carboxylic acid molecule can form two hydrogen bonds to another carboxylic acid molecule, producing a dimer. Dimers have twice the mass of a single molecule, and a higher temperature is needed to boil carboxylic acids than would be needed if no dimers were present. Copyright Houghton Mifflin Company. All rights reserved. 13 47

The boiling points of monocarboxylic acids compared to those of other types of compounds. All compounds in the comparison have unbranched carbon chains. Copyright Houghton Mifflin Company. All rights reserved. 13 48

Carboxylic acids react completely with strong bases such as NaH. The resulting carboxylate salts are converted back to the carboxylic acid with strong acids. H + NaH Na + + H 2 + NaCl HCl Carboxylic acids react with alcohols to produce esters. H + H + CH 3 H + H 2 Copyright Houghton Mifflin Company. All rights reserved. 13 50

Carboxylic acids react with amines to produce amides. H + high temp NH 3 NH + H 2 2 Amides will be discussed in more detail in sections 13.10 and 13.11. Copyright Houghton Mifflin Company. All rights reserved. 13 51

The simple esters are colorless, volatile liquids with a pleasant smell. Esters are neither acids nor bases in aqueous solution. An ester s name consists of two words. The name of the alkyl group in the ester group, -CR, and the name of the parent carboxylic acid with the family name oic replaced with ate; e.g. ethyl acetate: CH 3 (C=)CH 2 CH 3 acetate ethyl Copyright Houghton Mifflin Company. All rights reserved. 13 53

Esters To create an ester the H group of a carboxylic acid is replaced by an R group. Esters cannot form hydrogen bonds with each other. Therefore, esters have lower boiling points than the carboxylic acids from which they are derived. Copyright Houghton Mifflin Company. All rights reserved. 13 55

FRMING ESTERS FRM CARBXYLIC ACIDS The reactions of alcohols (R-H) and amines (R-NH 2 ) with carboxylic acids follow the same pattern both replace the H group in the acid with another group. Esterification: Esterification is carried out by warming a mixture of a carboxylic acid and an alcohol in the presence of a catalytic amount of a strong acid catalyst. This is an elimination reaction. Water is R-C-H + H-R R-C--R +H 2 split out acid alcohol ester water Copyright Houghton Mifflin Company. All rights reserved. 13 56

Aspirin and ther ver-the-counter Carboxylic Acid Derivatives Aspirin: A member of a group of drugs known as salicylates. Aspirin is an analgesic (relieves pain), antipyretic (reduces fever), and anti-inflammatory (reduces inflammation). Salicylates are esters of salicyclic acid. Early people knew that chewing willow bark could relieve pain. It was salicylic acid in the bark that caused the effect. But the acid was bitter and caused stomach problems. In 1897 German chemists at Bayer acetylated salicylic acid and gave the world Aspirin. Copyright Houghton Mifflin Company. All rights reserved. 13 57

Esterification = forward reaction (remove water) CH H + CH 3 CH H + heat CH salicylic acid acetic acid CH 3 aspirin Hydrolysis = reverse reaction = adding water to break a bond Copyright Houghton Mifflin Company. All rights reserved. 13 58

Amides Amides may contain an NH 2 group or one or both of the hydrogens can be replaced with alkyl groups. Unsubstituted amides, RCNH 2, can form three hydrogen bonds to other amide molecules and thus have higher melting and boiling points than the acids from which they are derived. Copyright Houghton Mifflin Company. All rights reserved. 13 61

Unsubstituted amides, RCNH 2, are named by replacing the oic acid by amide. Substituted amides are named by first specifying the alkyl group and then identifying the amide name. The alkyl substituents are preceded by the letter N to specify that the alkyl groups are attached to the nitrogen. Copyright Houghton Mifflin Company. All rights reserved. 13 62

Note on Naming These Compounds H- gives form- CH 3 -gives acet- HCH = formic acid HC - = formate ion H(C=)H = formaldehyde H(C=)NH 2 = formamide CH 3 -CH = Acetic acid CH 3 -C - = acetate ion CH 3 (C=)H = acetaldehyde CH 3 (C=)NH 2 = acetamide Examples: CH 3 (C=)CH 3 = acetone H(C=)N(CH 3 ) 2 = N,N-dimethylformamide CH 3 (C=)NH-CH 2 CH 3 = N-ethylacetamide acetamide ethyl Copyright Houghton Mifflin Company. All rights reserved. 13 63

NAIL PLISH SLVENTS CH 3 (C=)CH 3 = acetone CH 3 (C=)--CH 2 CH 3 = ethylacetate acetate ethyl The Merck Index: Caution: Inhalation may produce headache, fatigue, excitement, bronchial irritation, and, in large amounts, narcosis. Serious poisoning rare. Copyright Houghton Mifflin Company. All rights reserved. 13 64

Urea is a one-carbon amide. Its formation is the human body s primary method of eliminating nitrogen waste. The kidneys remove urea from the blood and provide a route for its excretion into the urine. When the kidneys malfunction, urea concentration builds up to toxic levels, a condition known as uremia. H 2 N NH 2 Note that urea is like acetone with the -CH 3 groups replaced by -NH 2 groups Copyright Houghton Mifflin Company. All rights reserved. 13 66

Tylenol Tylenol, a.k.a. acetaminophen, is an amide. HN H In this case the amine component is an aniline. The IUPAC name is N-(4-hydroxyphenyl)-acetamide. Copyright Houghton Mifflin Company. All rights reserved. 13 67

Amide Formation: Amides are formed by heating a mixture of a carboxylic acid and an amine. (The reaction is best accomplished by treating an acid chloride with ammonia or an amine.) Cl + NH 3 NH 2 + HCl Cl + NH 2 R N H R + HCl Cl + HN R' R R N R' + HCl Copyright Houghton Mifflin Company. All rights reserved. 13 69

Acetaminophen: An amide that also contains a hydroxyl group. It is best known as Tylenol. It is an alternative to aspirin for pain relief, but unlike aspirin it is not an anti-inflammatory agent. Copyright Houghton Mifflin Company. All rights reserved. 13 70

Hydrolysis of Esters and Amides Recall: Hydrolysis means the addition of water to split a bond. Esters and amides undergo hydrolysis to give back the carboxylic acid and alcohol or amine. Ester hydrolysis: Ester hydrolysis reactions can be catalyzed by either an acid or a base. + NaH Na + CH 3 H Copyright Houghton Mifflin Company. All rights reserved. 13 71

Acid catalyzed ester hydrolysis is simply the reverse of esterification reaction. In this reaction, an ester is treated with water in the presence of a strong acid catalyst such as sulfuric acid. Base catalyzed ester hydrolysis with a base such as NaH or KH is known as saponification. The product of a saponification reaction is a carboxylate anion rather then a free carboxylic acid. Copyright Houghton Mifflin Company. All rights reserved. 13 72

Amide hydrolysis: Amides are stable in water, but undergo hydrolysis when heated in the presence of a base or an acid. The products of amide hydrolysis reactions in the presence of a base or an acid are shown below. Copyright Houghton Mifflin Company. All rights reserved. 13 73

Errors in the Text Question 13.25(d). The ring part of the structure shown should be a phenyl (benzene) group., i..e., a hexagon with a circle inside. n page 353: In the Chemical Portrait the structure shown is actually acetaldehyde, not acetone. (The text is correct for acetone.) Acetone is CH 3 -(C=)-CH 3 Bonuses: Students who are first to point out any error in the text in the chapters we cover will receive a bonus of 2 points. Copyright Houghton Mifflin Company. All rights reserved. 13 74

CNDENSATIN PLYMERS These are formed by reacting difunctional monomers to give a polymer and a small molecule, usually water or HCl. Note: condensation is the reverse of hydrolysis. A polyester polymer is a condensation polymer in which the monomers are joined through ester linkages. H H + H H H H + H 2 diacid dialcohol Poly(ethylene terephthalate), a polymer = PET Copyright Houghton Mifflin Company. All rights reserved. 13 76

Polyamides and Polyesters Polymer molecules are composed of thousands of repeating units, known as monomers. Both polyamides and polyesters are polymers; they have many uses. Polyamides are formed by reaction between diamines and diacids. Nylons are polyamides. Polyesters are formed by reaction between diacids and dialcohols. Copyright Houghton Mifflin Company. All rights reserved. 13 77

A polyamide is a condensation polymer in which the monomers are joined through amide linkages. H 2 N 1,6-hexanediamine NH 2 + H hexanedioic acid H HN H N N H H N Nylon 66 Copyright Houghton Mifflin Company. All rights reserved. 13 78

PLYURETHANES Polyurethanes are polymers related to polyesters and polyamides. The backbone of a polyurethane polymer contains aspects of both ester and amide functional groups. H H N N N N N H H H Foam rubber in furniture upholstery (e.g. on airplanes), packaging materials, life preservers, elastic fibers, and many other products such as skin substitute membranes (Figure 13.13) contain polyurethane polymers. Copyright Houghton Mifflin Company. All rights reserved. 13 80

In the News The U.S. Environmental Protection Agency (EPA) has recently questioned the safety of perfluorooctanoic acid (PFA), a compound employed in making teflon and a variety of nonstick Items. PFA may be a carcinogen (a cancer-causing agent). What is the formula of PFA? Perfluoro means that all of the hydrogens attached to the carbons in the compound have been replaced by fluorine atoms. ctanoic acid is an organic acid with 8 carbons, thus PFA = CF 3 -(CF 2 ) 6 -CH Note that the acid hydrogen is not replaced by a fluorine. Copyright Houghton Mifflin Company. All rights reserved. 13 81

Chapter Summary Carbonyl compounds contain a carbonyl group (C=). Carbonyl groups are strongly polarized, with a partial positive charge on carbon and partial negative charge on oxygen. Carbonyl compounds are broadly divided into two groups: aldehydes and ketones are in one group and the second group contains carboxylic acids, esters, and amides. Copyright Houghton Mifflin Company. All rights reserved. 13 82

Chapter Summary (Cont d) Systematic or IUPAC names for aldehydes are derived by replacing e at the end of the name of the alkane with al. Ketones are named systematically by replacing the final e of the corresponding alkane name with one. Aldehydes and ketones do not form hydrogen bonds, as a result they have lower boiling points than alcohols of similar size. Copyright Houghton Mifflin Company. All rights reserved. 13 83

Chapter Summary (cont d) Aldehydes and ketones are soluble in common organic solvents, and those with fewer then five carbons are also soluble in water. Simple ketones are excellent solvents because they dissolve both polar and nonpolar compounds. Alcohols can be oxidized to aldehydes and ketones. Aldehydes can be further oxidized to carboxylic acids. Aldehydes are reduced to primary alcohols, and ketones are reduced to secondary alcohols. Copyright Houghton Mifflin Company. All rights reserved. 13 84

Chapter Summary (cont d) Most carboxylic acids are weak acids but esters and amides are neither acids nor bases. Carboxylic acids, esters, and amides undergo carbonyl group substitution reactions. Simple acids and esters are liquids; all amides except formamide are solids. In esters, the -H group in the acid is replaced by an -R group of an alcohol. In amides, the -H group in an acid is replaced by an NH 2 group of ammonia, or an NHR or NR 2 group of a primary or secondary amine. Copyright Houghton Mifflin Company. All rights reserved. 13 85

What you absolutely must know from Chapter 13 You must know the general forms of the following compounds: Aldehyde Ketone Carboxylic Acid Ester Amide How to name aldehydes, ketones, carboxylic acids, and esters. The common names of certain simple compounds: formaldehyde, acetone, formic acid, benzaldehyde, urea, formamide, acetamide, Some important reactions: --Primary alcohols can be oxidized to form aldehydes. --Secondary alcohols can be oxidized to form ketones. --Aldehydes can be further oxidized to form carboxylic acids. --Ketones resist oxidation --Esters can be hydrolyzed to form an alcohol and a carboxylic acid --Amides can be hydrolyzed to form an amine and a carboxylic acid (Hydrolysis = adding water to split up a compound) Copyright Houghton Mifflin Company. All rights reserved. 13 86

Chapter 13 (continued) Polymers are large compound formed by linking smaller units called monomers. Condensation polymers are formed by reacting difunctional monomers and splitting out small molecules (e.g., H 2 ): --A polyester is formed by the reaction of a diacid and a dialcohol: HC-R-CH + H-R -H HC-R-C--R -H + H 2 ester link --A polyamide (such as nylon) can be formed from the reaction of a diacid and a diamine: HC-R-CH + HHN-R -NH HC-R-C-NH-R -H + H 2 amide link Copyright Houghton Mifflin Company. All rights reserved. 13 87