Organic Chemistry

Question 1

Gas-Liquid Chromatography

Answer 1

A laboratory technique used to separate small quantities of molecules by their boiling points.

Gas-liquid chromatography can be used to determine the purity of a sample.

Question 2

Electrophile

Answer 2

An electron-poor molecule that can accept a pair of electrons.

Electrophile is synonymous with Lewis acid.

Question 3

Carbanion

Answer 3

A molecule containing a carbon atom with a negative charge

Carbanions are nucleophilic and have a tetrahedral geometry.

Question 4

Diastereomers

Answer 4

Stereoisomers that are non-superimposable non-mirror images.

Diastereomers have different chemical and physical properties.

Question 5

Monosaccharide

Answer 5

The simplest of carbohydrates and the building blocks of more complex sugars

Monosaccharides are also called single sugars and include glucose, fructose, ribose, and deoxyribose.

Question 6

Nucleophile

Answer 6

An electron-rich molecule that can donate a pair of electrons.

Nucleophile is synonymous with Lewis base.

Question 7

Absolute Configuration

Answer 7

The spatial arrangement of atoms around a chiral center.

The absolute configuration can be R or S.

Question 8

Anomeric Carbon

Answer 8

The anomeric carbon is the carbon that forms the new stereocenter during cyclization of a linear carbohydrate.

The anomeric carbon is also the carbonyl carbon in the linear form of the carbohydrate.

Question 9

Specific Rotation

Answer 9

A measure of how much a chiral compound rotates plane-polarized light.

Compounds that rotate plane-polarized light clockwise and counterclockwise are called dextrorotatory and levorotatory, respectively.

Question 10

Anomer

Answer 10

Cyclic carbohydrates that differ in absolute configuration only at the anomeric carbon but are otherwise identical.

Anomers are also epimers.

Question 11

Carbocation

Answer 11

A molecule containing a carbon atom with a positive charge

Carbocations are electrophilic and have a trigonal planar geometry.

Question 12

Column Chromatography

Answer 12

A laboratory technique used to separate large quantities of molecules by polarity.

In column chromatography, the less polar compounds elute first and the more polar compounds elute later.

Question 13

Structural Isomers

Answer 13

Isomers that differ in the way their atoms are bonded together.

Structural isomers are also called constitutional isomers.

Question 14

Stereoisomers

Answer 14

Isomers that differ in the spatial orientation of their atoms but have the same chemical bonds.

Stereoisomers include conformational isomers, diastereomers, and enantiomers.

Question 15

Glycosidic Linkage

Answer 15

A covalent bond that links two carbohydrate molecules.

The glycosydic linkage is named based on the absolute configuration of the anomeric carbon and the numbers of the carbon atoms involved in the linkage.

Question 16

Steric Hindrance

Answer 16

The inhibition of a chemical reaction due to the congestion of large substituents on the reactant molecules.

The larger the substituents, the more impact steric hindrance has on the rate of the reaction.

Question 17

Epimer

Answer 17

Diastreomers with chiral centers that differ in absolute configuration at only a single chiral center.

Glucose and galactose are epimers with the same absolute configuration at every chiral center except at the C-4 carbon.

Question 18

Distillation

Answer 18

A laboratory technique used to separate large quantities of molecules by their boiling points.

In distillation, the compound to be isolated is boiled off and collected, leaving the impurities that have higher boiling points behind. Sometimes, it is the impurity that is boiled off, leaving the compound of interest behind.

Question 19

Chiral Center

Answer 19

An atom bound to four different substituents.

Chiral centers are also called stereocenters and stereogenic centers.

Question 20

Conformational Isomers

Answer 20

Stereoisomers that differ in rotation about a single bond.

Conformational isomers are also called rotamers and conformers.

Question 21

High Performance Liquid Chromatography

Answer 21

A laboratory technique that uses high pressures to achieve higher quality separation of mixtures.

HPLC generally refers to a more advanced version of column chromatography but can also be applied to other forms of chromatography to enhance separation.

Question 22

Enantiomers

Answer 22

Stereoisomers that are non-superimposable mirror images of each other

Enantiomers rotate plane-polarized light by equal amounts but in opposite directions. Asides from optical activity, enantiomers have identical chemical and physical properties.

Question 23

Isomer

Answer 23

Compounds with the same chemical formula.

Despite containing the same atoms, isomers can have different chemical and physical properties.

Question 24

Thin-Layer Chromatography

Answer 24

A laboratory technique used to separate small quantities of molecules by polarity.

Thin-layer chromatography can be used to determine whether or not a reaction has gone to completion.