GLOSSARY L-Amino acid (Section 27. 2): a description of the stereochem Antibonding orbital(Section 1. 14): An orbital in a molecule in istry at the a-carbon atom of a chiral amino acid. The which an electron is less stable than when localized on ar Fischer projection of an a-amino acid has the amino group isolated atom on the left when the carbon chain is vertical with the car Anticodon (Section 27 28): Sequence of three bases in a mole boxyl group at the top cule of tRNa that is complementary to the codon of mRNA for a particular amino acid Anti-Markovnikov addition (Sections 6.8, 6.11): Addition re- H3N action for which the regioselectivity is opposite to that pre dicted on the basis of markovnikov's rul protic solvent(Section 8.12): A solvent that does not have Amino acid racemization (Section 27. 2)a method fc easily exchangeable protons such as those bonded to oxy- archeological samples based on the rate at which gen of hydroxyl groups geochemistry at the a carbon of amino acid compon Ar-(Section 2.2): Symbol for an aryl group randomized. It is useful for samples too old to be Arene(Section 2. 1 ) Aromatic hydrocarbon. Often abbreviated dated byC decay ArH Amino acid residues (Section 27.7): Individual amino acid Arenium ion( Section 12.2): The carbocation intermediate components of a peptide or protein formed by attack of an electrophile on an aromatic substrate Amino sugar (Section 25. 11): Carbohydrate in which one of in electrophilic aromatic substitution. See cyclohexadienyl the hydroxyl groups has been replaced by an amino group cation Amylopectin (Section 25. 15): A polysaccharide present in Aromatic compound (Section 11.3): An electron-delocalized starch. Amylopectin is a polymer of a(1, 4)-linked glucose species that is much more stable than any structure written units, as is amylose(see amylose). Unlike amylose, amy for it in which all the electrons are localized either in co lopectin contains branches of 24-30 glucose units con- lent bonds or as unshared electron pairs nected to the main chain by an a(1, 6) linkage. Aromaticity (Section 11.4): Special stability associated with Amylose (Section 25. 15): The water-dispersible component of aromatic compounds starch. It is a polymer of o(1, 4)-linked glucose Arylamine(Section 22.1): An amine that has an aryl group at- Anabolic steroid (Section 26. 15): A steroid that promotes mus ached to the amin Aryne (Section 23.8): A species that contains a triple bond Androgen (Section 26.15): A male sex hormone within an aromatic ring Angle strain (Section 3. 4): The strain a molecule possesses be- Asymmetric(Section 7.1): Lacking all significant symmetry cause its bond angles are distorted from their normal values elements; an asymmetric object does not have a plane, axis, Anion (Section 1. 2): Negatively charged ion. center of symmetry. Annulene (Section 11. 19): Monocyclic hydrocarbon character- Asymmetric center (Section 7. 2): Obsolete name for a ste ed by a completely conjugated system of double bonds neogenic center Annulenes may or may not be aromatic. Atactic polymer(Section 7. 15): Polymer characterized by ran- Anomeric carbon (Section 25.6): The carbon atom in a fura- dom stereochemistry at its stereogenic centers. An atactic nose or pyranose form that is derived from the carbonyl car- polymer, unlike an isotactic or a syndiotactic polymer, is bon of the open-chain form. It is the ring carbon that is not a stereoregular bonded to two oxygens. Atomic number(Section 1. 1): The number of protons in the Anomeric effect(Section 25.8): The preference for an elec nucleus of a particular atom. The symbol for atomic number tronegative substituent, especially a hydroxyl group, to oc- is Z, and each element has a unique atomic number. cupy an axial orientation when bonded to the anomeric car Axial bond (Section 3.6): a bond to a carbon in the chair con- bon in the pyranose form of a carbohydrate formation of cyclohexane oriented like the six "up-and Anti (Section 3. 1): Term describing relative position of two down"bonds in the following: substituents on adjacent atoms when the angle between their bonds is on the order of 180. Atoms X and y in the structure shown are anti to each other (Section 22 19): Formation of a compound of the =NAr by reaction of an aryl diazonium salt with The arene must be strongly activated toward elec- aromatic substitution; that is, it must bear a power ful electron-releasing substituent such as-OH or-NR, Anti addition ( Section 6.3): Addition reaction in which the tw portions of the attacking reagent X-Y add to opposite faces of the double bond Forward Main Menu TOC Study Guide Toc Student OLCMHHE WebsiteG-3 GLOSSARY L-Amino acid (Section 27.2): A description of the stereochem￾istry at the -carbon atom of a chiral amino acid. The Fischer projection of an -amino acid has the amino group on the left when the carbon chain is vertical with the car￾boxyl group at the top. Amino acid racemization (Section 27.2) A method for dating archeological samples based on the rate at which the ste￾reochemistry at the carbon of amino acid components is randomized. It is useful for samples too old to be reliably dated by 14C decay. Amino acid residues (Section 27.7): Individual amino acid components of a peptide or protein. Amino sugar (Section 25.11): Carbohydrate in which one of the hydroxyl groups has been replaced by an amino group. Amylopectin (Section 25.15): A polysaccharide present in starch. Amylopectin is a polymer of (1,4)-linked glucose units, as is amylose (see amylose). Unlike amylose, amy￾lopectin contains branches of 24—30 glucose units con￾nected to the main chain by an (1,6) linkage. Amylose (Section 25.15): The water-dispersible component of starch. It is a polymer of (1,4)-linked glucose units. Anabolic steroid (Section 26.15): A steroid that promotes mus￾cle growth. Androgen (Section 26.15): A male sex hormone. Angle strain (Section 3.4): The strain a molecule possesses be￾cause its bond angles are distorted from their normal values. Anion (Section 1.2): Negatively charged ion. Annulene (Section 11.19): Monocyclic hydrocarbon character￾ized by a completely conjugated system of double bonds. Annulenes may or may not be aromatic. Anomeric carbon (Section 25.6): The carbon atom in a fura￾nose or pyranose form that is derived from the carbonyl car￾bon of the open-chain form. It is the ring carbon that is bonded to two oxygens. Anomeric effect (Section 25.8): The preference for an elec￾tronegative substituent, especially a hydroxyl group, to oc￾cupy an axial orientation when bonded to the anomeric car￾bon in the pyranose form of a carbohydrate. Anti (Section 3.1): Term describing relative position of two substituents on adjacent atoms when the angle between their bonds is on the order of 180°. Atoms X and Y in the structure shown are anti to each other. Anti addition (Section 6.3): Addition reaction in which the two portions of the attacking reagent X±Y add to opposite faces of the double bond. X Y CO2  H3N H R Antibonding orbital (Section 1.14): An orbital in a molecule in which an electron is less stable than when localized on an isolated atom. Anticodon (Section 27.28): Sequence of three bases in a mole￾cule of tRNA that is complementary to the codon of mRNA for a particular amino acid. Anti-Markovnikov addition (Sections 6.8, 6.11): Addition re￾action for which the regioselectivity is opposite to that pre￾dicted on the basis of Markovnikov’s rule. Aprotic solvent (Section 8.12): A solvent that does not have easily exchangeable protons such as those bonded to oxy￾gen of hydroxyl groups. Ar± (Section 2.2): Symbol for an aryl group. Arene (Section 2.1): Aromatic hydrocarbon. Often abbreviated ArH. Arenium ion (Section 12.2): The carbocation intermediate formed by attack of an electrophile on an aromatic substrate in electrophilic aromatic substitution. See cyclohexadienyl cation. Aromatic compound (Section 11.3): An electron-delocalized species that is much more stable than any structure written for it in which all the electrons are localized either in cova￾lent bonds or as unshared electron pairs. Aromaticity (Section 11.4): Special stability associated with aromatic compounds. Arylamine (Section 22.1): An amine that has an aryl group at￾tached to the amine nitrogen. Aryne (Section 23.8): A species that contains a triple bond within an aromatic ring (see benzyne). Asymmetric (Section 7.1): Lacking all significant symmetry elements; an asymmetric object does not have a plane, axis, or center of symmetry. Asymmetric center (Section 7.2): Obsolete name for a ste￾reogenic center. Atactic polymer (Section 7.15): Polymer characterized by ran￾dom stereochemistry at its stereogenic centers. An atactic polymer, unlike an isotactic or a syndiotactic polymer, is not a stereoregular polymer. Atomic number (Section 1.1): The number of protons in the nucleus of a particular atom. The symbol for atomic number is Z, and each element has a unique atomic number. Axial bond (Section 3.6): A bond to a carbon in the chair con￾formation of cyclohexane oriented like the six “up-and￾down” bonds in the following: Azo coupling (Section 22.19): Formation of a compound of the type ArNœNAr by reaction of an aryl diazonium salt with an arene. The arene must be strongly activated toward elec￾trophilic aromatic substitution; that is, it must bear a power￾ful electron-releasing substituent such as ±OH or ±NR2.