Most carbon compounds are called organic compounds while others are called inorganic compounds. The historic reason for the name was the mistaken idea that living matter, organic matter, was chemically different from nonliving matter (inorganic matter). We now know that organic compounds, the vast majority of all compounds, can be synthesized not only by the natural processes of living organisms, but also in the laboratory without the help of living things.
The principles of chemistry presented in this text apply equally to inorganic chemistry (general chemistry), organic chemistry, and biochemistry. This chapter has been included because of the needs of those students who are headed toward the biologically oriented fields of study and the increasing incidences of organic examples included in inorganic texts (those for General Chemistry). Also, many academicians consider organic processes to be different, which they really aren’t! We will briefly cover a selection of the more important chemical reactions, special nomenclature (naming and/or identification) of isomerism, attention to the details of isomerism, and some examples from biochemistry.
Carbon atoms are capable of forming strong bonds with each other, which leads to many organic compounds typically having a large number of atoms per molecule with a variety of ways the atoms can connect. The naming system for organic compounds must indicate the number of carbon atoms and the pattern of the atoms’ connections. Hydrocarbons are the compounds that are composed of only hydrogen and carbon. If there are no multiple bonds, these are called alkanes, and if there are no ring structures, they have the empirical formula CnH2n+2 in order to satisfy the rules for bonding as in Chapter 9. The name of an organic compound generally provides the number of carbon atoms. The root of the name indicates the number of carbons—meth meaning one, eth for two, prop for three, but for four, pent for five, hex for six, etc. The number of atoms of other elements is often implied. For instance, in cyclic compounds each ring of carbon atoms reduces the number of hydrogens by 2; each double bond (alkenes or olefins) also reduces hydrogens by 2; and each triple bond (alkyne) reduces hydrogens by 4.
In older, less systematic nomenclature, the root counted all the carbons. As an example, “butane” meant C4H10, with the suffix (word ending) ane indicating an alkane. However, there is more than one structure with C4H10, which is really a simple count of atoms. There could be the straight chain of carbon or there could be a chain of three carbons with one branching off the center carbon as shown.
This style of sketching assumes carbon atoms at each end of line and at each intersection of lines. Also, the hydrogens are left out with sufficient hydrogens assumed to complete the four bonds to each carbon. Note that iso is added to “butane” to indicate a branched structure. This system will not work if there are more than four carbons because there are too many possible isomers to allow for convenient naming.
The International Union of Pure and Applied Chemistry (IUPAC) adopted a system that is clear. For noncyclic alkanes, the root gives the number of carbons in the longest chain. Each branch is described by a prefix indicating the number of carbons in the branch, and a number indicating the point of connection to the longest chain. (Numbering starts at the end of the chain which produces the smallest numerals.) The IUPAC names for the structures above are “butane” and “2-methyl propane.”
EXAMPLE 1 Before the IUPAC rules were developed, “hexane” would have been the name of both compounds. Note the IUPAC names for these structures:
The naming system is extended to include alkenes by changing the suffix from -ane to -ene, and to alkynes by the suffix -yne. A number before the suffix gives the location of the multiple bond. The terminal carbon is that closest to the multiple bond; it has priority over branching of the carbon skeleton.
EXAMPLE 2 Provide the IUPAC names for these hydrocarbons. (Notice that this is another style of sketching that is a type of shorthand for the locations of the hydrogens.)
The prefix cyclo- appears before the root of the name in ring compounds, except for those involving the benzene ring (Problem 9.9). The benzene compounds form a special category of compounds referred to as aromatic compounds. The opposite of aromatic is aliphatic. Further modifications of the system, such as those when elements other than carbon and hydrogen are involved, will be noted when functional groups are discussed.
In keeping with the principles and definitions in Chapter 9, isomers are compounds with the same number of atoms of each kind per molecule, but they are different substances because of differences in molecular structure. There are three classes of isomers: structural, geometric, and optical.
Structural isomerism is when the molecules differ in the sequence of atomic attachments in the skeleton of the molecule. The compounds in Example 1 are structural isomers. The IUPAC names clearly state the difference between compounds with the same molecular formula, but different structures.
Geometric isomerism occurs when the three-dimensional shape of the molecules differs. This occurs when a significant part of the molecule is rigidly fixed because of the presence of a double bond or a ring. In simple cases, geometrical isomers can be distinguished by their names containing cis- or trans- according to whether two groups are on the same side (close) of the double bond or on opposite sides (far apart).
Optical isomerism is when two molecules are nonsuperimposable mirror images of each other (Think of apair of gloves. They can only stack palm to palm, not one on top of the other.) Such molecules are termed asymmetric or chiral. (Note: Chiral carbons have 4 different substituents.) Two optical isomers can be distinguished in their names by the prefixes dextro- or levo- according to whether a solution of the compound rotates a beam of polarized light to the right or the left. The abbreviations D- and L- are commonly used for dextro- and levo-. A new system of naming uses R- (rectus) and S- (sinister).
EXAMPLE 3 Draw the geometric isomers of 2-butene. (b) Draw the optical isomers of 1-bromo-1-chloroethane.
(a) Because of the double bond, all atoms except the six end-hydrogens are found only in one plane, which we chose as the plane of the paper.
(b) If both carbons and the bromine are placed in the plane of the paper, the chorine and hydrogen atoms are on opposite sides of the plane with their bonds to carbon forming approximately 109° angles to the other bonds of that carbon atom. Relative to the plane of the paper, chlorine is shown toward you and the hydrogen away from you.
Alkanes are somewhat nonreactive and their chemistry is not very interesting. But if a multiple bond is formed on the loss of hydrogens or an atom is substituted for a hydrogen, characteristic properties and reactions result. These properties do not depend on the number or arrangement of carbon atoms in the rest of the molecule. A group of atoms that determines these properties of the compound is called a functional group. Learning the properties and reactions of the functional groups simplifies the study of organic chemistry. Table 15-1 lists some of the common functional groups. In the case of acids, acid is added in addition to the suffix -oic. The word ether appears separate from the rest of the name, and esters have a two-part name indicating the structures of the two parts of the molecule joined by the ester group.
Aldehydes, acids, and esters have roots for one and two carbons that are usually form- and acet-, rather than meth- and eth-, because these prefixes had been used so long they were grandfathered into the naming system (formaldehyde and acetic acid, rather than methanal and ethanoic acid). Departures from IUPAC nomenclature often occur for very common substances and, fortunately, they rarely can be misunderstood (ethyl alcohol instead of ethanol).
Alkanes are colorless, insoluble in water, have low boiling points, and are commonly used as fuels (butane, propane, octane, etc.). Combustion (usually, burning in oxygen) reactions (alkane + O2) yield CO2 and H2O and may produce some CO (C2+) if there isn’t sufficient oxygen present to produce the C4+ oxidation state. The reaction of alkanes with halogens (F, Cl, Br, and I) can be controlled, resulting in the substitution of a halogen for a hydrogen without disruption of the carbon skeleton.
Alkenes are similar to alkanes in structure and also undergo combustion. However, they are much more likely to undergo addition reactions with halogens, rather than substitution. Addition reactions occur with a wide variety of reagents.
A very important reaction, especially in the plastics industry, is additional polymerization, in which alkene molecules add to themselves to form long chains. As an example, a polymerization of CH3CH = CH2 results in the production of
The halogens are F, Cl, Br, and I. Halogenated compounds are water-insoluble and have higher boiling points than the corresponding hydrocarbon. They find wide use as solvents, cleaning fluids, insecticides, refrigerants, and (when in polymers) as plastics. They are also important starting materials for the synthesis of other compounds since the halogen can be replaced with OH (using NaOH) and other groups.
Many alcohols have a definite scent as the small (low mass) alcohols evaporate at room temperature. Water solubility and high boiling point for the relative size of the molecules are due to extensive hydrogen bonding. Two very important condensation reactions are (a) with another alcohol molecule to form an ether, and (b) with an acid to form an ester (esterification produces an organic salt). A condensation reaction in general is one in which two molecules become joined with the elimination of water or some other small molecule. Esterification can be reversed by means of hydrolysis, the reaction with water in which the original acid and alcohol are recovered. If an ester happens to be a natural fat, the process of its production is saponification since the sodium salt of the acid is a soap. The specific reaction that occurs, including condensation and hydrolysis, is quite dependent on the reaction conditions including temperature, pH, and presence of a catalyst.
There are groupings of atoms that act together and are called functional groups. For example, methyl alcohol (methanol) contains the methyl group, —CH3, derived from methane, CH4. Similarly, other function groups can be derived from other alkanes by the loss of one hydrogen atom; these groups are the alkyl groups. An alkyl group can accept various atoms to replace the hydrogen including chlorine, bromine, and iodine. There are other groups that can replace the hydrogen, such as the alcohol group (—OH), carboxyl group (—COOH), and others. Each of these atoms or groups replacing the hydrogen contributes to the nature of the compound.
Aldehydes and ketones have much lower boiling points and are less water-soluble than the corresponding alcohols. In all cases, whether alcohols, aldehydes, ketones, or acids, water solubility gradually decreases as the number of carbon atoms increases within each class of compounds.
An alcohol can be viewed as the product of the first step in the oxidation of a hydrocarbon because there is an oxygen atom inserted between a carbon and a hydrogen. The addition of oxygen (or insertion) is one of the definitions of oxidation. If another oxygen atom is inserted on the same carbon and water is eliminated, the result is an aldehyde (if the carbon is at the end of the chain) or a ketone (if the carbon is in the middle of the chain). Inserting one more oxygen on the carbon of an aldehydes results in an acid—this is a carboxylic acid with the affected carbon often referred to as a carboxylic carbon (—COOH).
Short-chain carboxylic acids are quite soluble in water and tend to ionize slightly (typically, a few percent depending on concentration). These acids undergo the typical acid-base reactions. Besides the condensation reaction with alcohols, acids condense with ammonia or amines to form amides.
Salts of carboxylic acids and inorganic bases (KOH, NaOH, etc.) are fully ionized in the solid state and in aqueous solution. Salts of fatty acids (from hydrolysis of fats) with an inorganic base are soaps.
Amines can be considered derivatives of ammonia, NH3, in which one or more of the hydrogen atoms is replaced by an organic group, such as an alkyl group. The example in Table 15-1 is a primary amine (one H replaced); replacement of two H atoms is a secondary amine; replacement of all three results in a tertiary amine. Amines are somewhat soluble in water in which, like ammonia, they take up a proton leaving the solution basic. They dissolve readily in strong acid forming salts similar to ammonium salts.
The condensation of a carboxylic acid with ammonia or an amine yields an amide. The amide in Table 15-1 resulted from the condensation of propanoic acid with ammonia. The example in the preceding section involved the condensation of acetic acid with a primary amine. A very important class of biochemical molecules are the amino acids, which join to form protein molecules by the condensation of the amine group of one molecule to the acid group of the next. The amide linkage in this case has the special name peptide.
When an alcohol is heated under proper conditions with concentrated sulfuric acid, water is eliminated by the condensation of two molecules of alcohol and the combining groups, which may be alkyl groups. The groups are joined through an oxygen atom forming and ether. The product formed from ethanol, diethyl ether, is the familiar “ether” known for its use as a general anesthetic dating from the 1800s. Mixed ethers, such as methylethyl ether, may be formed by a condensation reaction of two, different alcohols. Ethers are only very slightly soluble in water, but are very good solvents for many other organic substances.
As discussed under alcohols, esters are the condensation products of alcohols and acids They are generally good organic solvents and are insoluble in water. Many found in nature are flavorful and sweet-smelling—amyl acetate is the fragrant component of banana oil ("amyl” is a traditional name for a five-carbon group). Natural fats and oils are esters of glycerol, a triol (3—OH groups), and fatty acids.
Benzene and compounds containing the benzene ring are the aromatic compounds. These compounds have somewhat different chemical properties than their aliphatic counterparts. For instance, the hydroxyl group (alcohol group) attached to a benzene ring is a weak acid (although much weaker than the carboxylic acid). The three alternating double bonds of the benzene ring are not readily saturated (containing no multiple bonds—the multiple bonds are broken and hydrogen bonded). If benzene is treated with chlorine (in the dark), substitution will occur, rather than addition.
Functional groups on the aliphatic side-chains attached to aromatic rings behave in a manner typical of aliphatic compounds.
Many molecules contain more than one function group (either the same or different). In such cases, condensation reactions involving two or more groups per molecule can lead to the formation of polymers, as mentioned above in the formation of proteins from amino acids (—NH2 and —COOH groups). From the standpoint of terminology, the unit or units that are joined together to produce a polymer are monomers with multiple units possible (dimer, trimer, etc.). An example of a man-made polymer involves the synthesis of polyester fiber, such as Dacron® polyester on which the textile industry depends.
Thousands of molecules of each reagent combine, eliminating a water molecule for each condensation forming the ester linkages. Note that the reaction, if continued, could theoretically form a molecule infinitely long.
Below is a listing of some of the factors that are special when considering biochemistry, the chemistry of living things.
1. As discussed directly above, molecules may be very large, but unlike a synthetic polymer, a biopolymer usually has a definite number and sequence of monomer units. Often, there is a fixed three-dimensional shape.
2. Classes of molecules are based primarily on structure, but also on their function in the living cell.
3. Reactions occur at a modest temperature and extremely sensitive catalysts (enzymes) are usually required. The energy to drive one reaction may come from the energy released by another reaction forming a sequence of reactions.
4. Throughout the animal and plant kingdoms, there is little or no difference in the structures of molecules that perform a given biological function.
As there are classes of organic molecules, there are also classes of biochemical molecules.
Proteins are polymers produced from amino acids that are joined by peptide linkages (amine-group carboxylic acid bonds). These compounds form the bulk of living tissue. Enzymes, those very selective and powerful catalysts, are also proteins. Enzymes may contain a group based on a metal atom, as may molecules from other classes of compounds (hemoglobin, chlorophyll, etc.). Some proteins serve special functions, such as hemoglobin, an oxygen carrier.
Carbohydrates that are sugars consist of relatively small molecules typically based on four to six carbons atoms in the skeleton. Sugars have hydroxyl and aldehyde or ketone functional groups. These molecules may function as fuels or as building blocks (monomers) for polymeric materials. Plants contain polymers of sugars called starch and cellulose formed by ether linkages. These polymers store energy (starches) and provide for rigid structure (cellulose).
Fats are esters of glycerol and the fatty acids. In plants, may of the fats are unsaturated (containing double bonds in the carbon skeleton) and liquid (oils). Fats also function as fuels, but for long-term energy storage, rather than the short-term storage and quick delivery of energy provided by sugars and starches. Fats are part of a class of compounds called lipids based on their insolubility in water and solubility in ether. Among other lipids are cholesterol and some materials important in the construction of cell membranes.
Nucleic acids are large polymers joined by ester linkages between phosphate and sugar monomer units (deoxyribose in DNA, and ribose in RNA). These sugars carry nitrogen-containing side-chains called purines or pyramidines, both referred to a nitrogen bases. The monomers, then, contain a phosphate, a sugar, and one nitrogen base. The monomers are joined with a phosphate of one linking to a point on the sugar of another. This system holds the nitrogen bases in a definite sequence along the molecule that constitutes the genetic code (DNA) of an individual organism and controls the sequencing of amino acids during the synthesis of proteins (DNA and RNA), as well as other functions.
15.1. Name each of the following compounds according to the IUPAC rules:
(a) The difficulty is the manner in which the structure is drawn. Find the longest chain, which is six carbon atoms, and start the numbering at the left to minimize the numbers indicating the points of substation: 2,4-dimethylhexane.
(b) The ring carbons are numbered so as to minimize the sum of the numbers: cyclohexa-1,3-diene.
(c) Chloro is treated as a prefix, but the carbonyl oxygen as a suffix: 1-chloro-3-pentanone.
(a)
(b)
(c)
(d)
(e)
(f)
(d) The compound is an ester. Contrary to the example in Table 15-1, the alcohol residue is to the left. In either case, the alcohol part is always named first: 2-methylpropyl ethanoate (or acetate).
(e) This compound is a secondary amine: methlypropylamine.
(f) The 18-carbon carboxylic acid reacted to form this compound is stearic acid, making the compound 2,3-dihydroxypropyl stearate. The alcohol residue is glycerol. Since only hydroxyl is esterified, this type of ester is called a monoglyceride and the compound may be named monoglyceryl stearate. It is valuable in food processing as an emulsifier.
15.2. Identify all the isomers with C5H10 as their formula. Provide the IUPAC names.
(a) Cyclopentane
(b) Methylcyclobutane
(c) 1,2-Dimethylcyclopropane
(d) 1,1-Dimethylcyclopropane
(e) Ethylcyclopropane
(f) 1-Pentene
(g) 2-Pentene
(h) 2-Methyl-1-butene
(i) 2-Methyl-2-butene
(j) 3-Methyl-1-butene
There is the possibility of cis-trans isomerism. The only case among the alkenes is (g), as below.
Structure (c) also shows cis-trans isomerism. The three carbons in the ring define a plane, the plane of the paper. Either both hydrogens of the CH groups are on the same side of this plane or one is above and the other below.
Structure (c) is also the only one which has a chiral carbon atom (the carbons of the two CH groups). However, the cis isomer has a plane of symmetry and cannot have an optical isomer. Only the trans isomer has an optical isomer.
15.3. Draw all of the structural isomers with the formula C3H6O. Point out any that have geometrical or optical isomers. (Not all structures satisfying Lewis rules correspond to stable chemical substances.)
15.4. Draw the structure of the organic produce results from each of these reactions.
(a) 1-Propanol in dehydrating medium.
(b) 1-Propanol in mildly oxidizing medium.
(c) 2-Propanol in mildly oxidizing medium.
(d) 1-Propanol plus butanoic acid in dehydrating medium.
(e) 1-Propanol plus metallic sodium.
(a) A condensation results in the elimination of water and the formation of an ether.
(b) One stage of oxidation of a hydroxyl group produces a carbonyl carbon (—C = O). When the alcohol is at the end of the chain (primary alcohol), the product is an aldehyde.
(c) When the alcohol is not at the end (secondary alcohol in this case), the product is a ketone.
(d) A condensation results in the elimination of water and the formation of an ester.
(e) Considering the alcohol to be a derivative of water, one expects the sodium to displace the hydrogen of the hydroxyl group. One product is H2; the other is the sodium salt of the alcohol.
15.5. Using structural formulas, describe these reactions.
(a) Vinyl chloride (alternate name: chloroethene) is treated with a polymerization catalyst.
(b) The amino acid alanine (2-aminopropanoic acid) is treated with the appropriate polymerase and the energy source to cause it to polymerize.
(a) The product is a saturated polymer since the double bonds have been used up in joining the monomers together to form polyvinyl chloride (PVC used to make plastic pipes and other materials).
(b) Water is removed, H from the amino group of one molecule and OH from the acid of the next, and polyalanine is formed. The boxed area encloses the peptide linkage formed between monomers.
15.6. List the IUPAC name of each of these compounds:
(a)
(b)
(c)
(d)
(e)
(f)
Ans. (a) 2-methylbutane; (b) 2,3-dimtheylpentane; (c) methylcyclohexane; (d) 2-pentene; (e) 3-methyl-1, 5-hexadiene; (f) 2-butyne
15.7. Name each of the following using the IUPAC system.
(a)
(b)
(c)
(d)
(e)
(f)
Ans. (a) methyl ethyl ether; (b) 2-chlorobutane; (c) cyclopropyl acetate (or ethanoate); (d) 3-methyl-1-pentanol; (e) triethylamine; (f) 2-pentanone
15.8. Name each of the following using the IUPAC system.
(a)
(b)
(c)
(d)
(e)
(f)
Ans. (a) propanal; (b) formamide (methanamide); (c) 3-ethylpentanoic acid; (d) N-ethylpropanamide; (e) benzene; (f) 1,2-dichlorobenzene
15.9. Draw the structures of the following compounds: (a) 3-ethyl-4-methyl-2-hexanone; (b) 2-chloro-buytl acetate; (c) ethylbenzene; (d) 3-ethylcyclohexene; (e) 2-methyl-3-pentanol; (f) 2-methylpropyl methyl ether.
(a)
(b)
(c)
Ans.
(d)
(e)
(f)
15.10. Explain what is wrong with each of the following names: (a) 3-methyl-2-propanol; (b) 3,3-dimethyl-2-pentene; (c) 1,4-dichlorocyclyobutane; (d) 2-propanal; (e) 2-methyl-1-butyne; (f) pentanoicacid.
Ans. (a) The longest chain is four carbons. The correct name is 2-butanol. (b) Such a compound is impossible because it would require five bonds on the third carbon. (c) Positions 1 and 4 are equivalent to 1 and 2. The correct name is 1,2-dichlorocyclobutane. (d) Such a compound is not possible because the aldehyde carbon must be at the end of the chain. (e) Such a compound won’t work because it would require five bonds on the second carbon. (f) The suffix “acid” should be a separate word. The correct name is pentanoic acid.
15.11. Draw the structures of all the structural isomers having the formulas: (a)C4H9Br; (b)C4H8;(c)C2H4O2(omit any peroxides,—O—O—); (d)CgH14;(e)C4HgCl2.
Ans.
(a)
(b)
(c)
Note: Not all the compounds above may be stable. The structure with two hydroxyl groups on the same carbon does not occur.
(d)
(e)
15.12. Examine all the answers to Problem 15.11 and select all that exhibit geometric isomerism, pointing out the two carbon atoms involved in each.
Ans. 
15.13. Examine all the answers to Problem 15.11 and select all that exhibit optical isomerism, pointing out the chiral carbon (or carbons) involved in each.
Ans.
15.14. Draw the structure for the smallest noncyclic alkane that has a chiral carbon and mark that carbon. Name the compound.
Ans. 
15.15. Natural rubber is a polymer of isoprene and has the following structure:
There is another product called gutta-percha, which is a geometric isomer of rubber, but is useless as an elastomer. Draw its structure and identify which is cis and which is trans.
Ans. Natural rubber is cis; gutta-percha is trans.
15.16. Which has more isomers, (a) dimethylbenzene or (b) dimethylcyclohexene? Explain.
Ans. Because all corners of the benzene ring are equivalent, (a) has only three isomers (structural) with the methyl groups in positions 1,2; 1,3; or 1,4. However, (b) can have many more structural isomers; for example, 1,2 is different from 1,6 and 1,3 is different from 2,4. There are also many geometric isomers; for example, the 3,4 structural isomer must have cis and trans forms. Optical isomerism also occurs; for instance, both carbons 3 and 4 of the 3,4 isomer are chiral.
15.17. Name the functional group in each of the following molecules:
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
(k)
(l)
Ans. (a) alcohol (hydroxyl); (b) amine (tertiary amine); (c) ester; (d) chloride; (e) ketone; (f) carboxylic acid; (g) ester (triglyceride); (h) amide; (i) ether; (j) aldehyde; (k) bromide (dibromide); (l) alkyne (triple bond)
15.18. Draw the structures for the following compounds: (a) butanamide; (b) methylpropylamine; (c) diethyl ether; (d) 2,3-dimethyl-1-hexanol; (e) ethyl 2-methylpropionate; (f) 3-iodo-2-pentanone.
(a)
(b)
(c)
Ans.
(d)
(e)
(f)
15.19. Draw the structure of the polymer formed by addition polymerization of 2-methyl-1-propene.
Ans.
15.20. What are the main products of the following reactions? Give the structures of the organic products.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
Ans.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
15.21. Draw a portion of the polymer formed by condensation of 1,2-ethanediol and maleic acid (IUPAC name: cis-butenedioic acid). This, and similar polymers, are copolymerized with styrene to form the “polyester resins,” which are widely used to make structural plastic moldings.
Ans. 
15.22. Formaldehyde (methanal) can form addition polymers. Imagine adding a water molecule to a methanal molecule to form a diol, which then forms an ether linkage with a similar neighboring molecule (splitting out water) and so on. Draw a portion of the resultant product.
Ans. 
15.23. “Silicones” are polymers that find widespread uses from high-temperature hydraulic fluids to medical prostheses. Draw a portion of the polymer formed by condensing out water from dimethylsilanediol, (CH3)2Si(OH)2.
Ans. 
15.24. Two carboxylic acid groups can combine by condensing out a water molecule to form an acid anhydride. Draw the structures of (a) acetic anhydride, which involves two molecules, and (b) maleic anhydride (see Problem 15.21), in which only one molecule is involved.
15.25. Adenosine triphosphate, ATP, is an extremely important molecule because it stores energy that is released as needed for energy for living organisms. (a) If there is a chiral carbon in ATP, identify that carbon by the number provided in the sketch (b) Considering the structure and composition of ATP, identify the elements involved at the points of the strongest negative charges. (c) If there are any, identify carbons that are substituted with an alcohol group. (d) This compound contains three rings. Identify which of the three rings, if any, are heterocyclic.
Ans. (a) The chiral carbons are 2, 3, 4, and 5 (four different substituents). (b) Both nitrogen and oxygen are expected to be negative points; however, the oxygens that are doubly bound to the phosphorus in the three phosphates are the most negative points. There are oxygens that are negative poles in the alcohol groups (—OH). It is true that there are nitrogens that service a negative pole, but the oxygens are more electronegative, eliminating the nitrogens from consideration. (c) #3 and #4; (d) All three rings are heterocyclic because they contain at least one atom other than carbon (N and O in these rings).
