Review of Functional Groups

Knewton’s Content Team Review of Functional Groups

Page 1

  • Knewton’s Content Team Review of Functional Groups
  • ACHIEVEMENT WITHIN REACH | 1
  • Table: Part 1

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  • Universities and Professors: Knewton’s Content Team Review of Functional Groups
  • ACHIEVEMENT WITHIN REACH | 2
  • Table: Part 2

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  • Cyclic Compounds
    • Organic compounds can be cyclic (rings).
    • Like acyclic organic compounds, they are named based on the number of carbons in the ring, but in addition, "cyclic" is placed in front.
    • Cyclic Alkanes:
    • Cyclopropane
    • Cyclobutane
    • Cyclopentane
    • Cyclohexane

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  • Cyclic Alkanes (continued):
    • Methylcyclopentane
    • Methylcyclohexane
    • 1,2-dimethylcyclohexane
    • 1,3-dimethylcyclohexane
    • cis-1,2-dimethylcyclohexane
    • trans-1,2-dimethylcyclohexane

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  • Cyclic Alkenes:
    • Cyclopentene
    • Cyclohexene
    • 1-Methylcyclohexene
    • 1,2-dimethylcyclohexene
    • 1,6-dimethylcyclohexene

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  • Cyclic Alcohols:
    • Cyclopropanol
    • Cyclobutanol
    • Cyclopentanol
    • cis-2-methylcyclohexanol
    • Cyclohexanol
    • 2-Methylcyclohexanol
    • trans-4-methylcyclohexanol

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  • Cyclic Ketones:
    • Cyclopentanone
    • Cyclohexanone
    • 2-Methylcyclopentanone
    • 2-Methylcyclohexanone
    • 4-Methylcyclohexanone

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  • Carbohydrate Structures and Classifications

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  • Carbohydrates in Biochemistry Assignment:
    • Carbohydrate Structures and Classifications
    • ACHIEVEMENT WITHIN REACH | 9

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  • Carbohydrates: Instruction
    • Carbohydrates are made of sugar.
    • The name carbohydrate comes from carbon (carbo-) and water (-hydrate).
    • Simple carbohydrates are represented by the formula:
    • (CH2O)n(CH_2O)_n, where n is the number of carbons.
    • Complex carbohydrates vary but remain close to this formula.
    • Differentiate between types of carbohydrates.

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  • Carbohydrates: Instruction (continued)
    • There are three subtypes of carbohydrates based on the number of individual simple sugar units used to form them:
    • Monosaccharides
    • Disaccharides
    • Polysaccharides

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  • Monosaccharides
    • Definition: Monosaccharides are simple sugars made of only one molecule.
    • Examples include:
    • Glucose
    • Fructose
    • Galactose
    • Mannose
    • Ribose
    • Glucose (C6H12O6C_6H_{12}O_6) is the most common monosaccharide and an important source of energy.
    • Most names end in suffix -ose.

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  • Stereochemistry of Sugars
    • Sugars with an aldehyde (R-CHO) group are aldoses.
    • Sugars with a ketone (R-C(O)-R’) group are ketoses.

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  • Sugars are also classified by the number of carbons in their structure.

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  • Example Problem
    • Question: How many carbons and what kind of functional groups are present in a ketohexose?
    • Solution: The name “ketohexose” indicates that the molecule is a sugar (“-ose”) containing six carbons (“-hex- ”) and a ketone carbonyl group (“keto-”).
    • Sugars also have hydroxyl groups attached to all the non-carbonyl carbons in the molecule.

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  • Carbohydrate Chemistry Assignment:
    • Carbohydrate Structure and Chirality

Page 17

  • Chirality: Instruction
    • Identify chiral carbon atoms and chiral molecules.
    • Definition of Chirality: Chirality is a property whereby an object is asymmetrical in a way that PREVENTS it from being superimposed on its mirror image.
    • CHIRAL

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  • Achirality
    • Definition: Achiral objects CAN be superimposed on their mirror images.
    • ACHIRAL

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  • Molecular Geometry and Chirality
    • Molecular geometry determines whether molecules are chiral or achiral.
    • Carbons attached to four different atoms or groups are chiral; chiral carbons are also called chiral centers.
    • Element “X” is usually carbon (C).
    • There must be 4 different groups bonded to “X” for the center to be chiral.

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  • Drawing Bonds Around Chiral Centers
    • Bonds around a chiral center are drawn to indicate their positions in 3D:
    • Solid lines = bond within the plane of the paper or screen.
    • Wedges = bond coming out toward the viewer.
    • Dashed lines = bond receding away from the viewer.
    • Visual representation of bonds indicates the orientation of groups around the chiral center.

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  • General Rules for Chirality
    • If the molecule contains 1 chiral carbon, the molecule is chiral.
    • If the molecule contains 2 or more chiral carbons, it may be chiral or achiral.
    • Molecules that lack a plane of symmetry within the molecule are chiral.
    • Molecules that have a plane of symmetry within the molecule are achiral.

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  • Stereoisomers and Enantiomers
    • Definition: Stereoisomers have the same molecular formula and the same sequence of connections but differ in their spatial arrangement.
    • Definition: Enantiomers are nonsuperimposable mirror images of each other and are a type of stereoisomer.
    • Enantiomers possess the same chemical and physical properties except for their interactions with chiral molecules and the rotation of plane polarized light.

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  • Chirality Practice
    • Solution: The chiral center is identified by an *.
    • Question: Identify any chiral centers in the structure below.

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  • Chirality Practice (continued)
    • Question: Identify all chiral centers in the structure below.
    • Solution: The chiral centers are identified with *.

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  • Fischer Projections: Instruction
    • Fischer projections are a way of drawing the structure of enantiomers or stereoisomers that conveys the 3D arrangement of the atoms.
    • Commonly used for monosaccharides, it allows easy visualization of multiple chiral carbons in a single molecule.
    • Fischer projections are simple to draw as they are similar to an expanded structural formula.

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  • Fischer Projections: Instruction (continued)
    • Example Fischer projections illustrate the difference in stereochemistry.

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  • Rules for Drawing Fischer Projections
    • The main carbon chain is written vertically with bonds assumed to be bending into the plane of the structure (i.e., dashed bonds).
    • The arrangement is such that the most oxidized carbon is as close to the top as possible.
    • Other atoms/groups are added by horizontal bonds that come out of the plane of the structure (i.e., wedge bonds).

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  • Continued Rules for Fischer Projections
    • All bonds are drawn at 90 degrees unless the central carbon is achiral.
    • Carbon atoms are numbered sequentially from the top of the molecule.

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  • Use of Fischer Projections
    • Fischer Projections are utilized to distinguish monosaccharide enantiomers by examining the last chiral carbon in the chain.
    • If the –OH group is on the right, the molecule is a D sugar.

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  • Continued Use of Fischer Projections
    • If the –OH group is on the left, the molecule is an L sugar.
    • Biochemistry has evolved to use D sugars exclusively.

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  • Fischer Projections: Practice
    • Question: Draw the Fischer projection for the enantiomer of the molecule shown below.
    • Solution: Complete the Fischer projection.

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  • Fischer Projections: Practice (continued)
    • Solution: Carbon 4 is the last chiral carbon; it indicates this is the D sugar.
    • Question: What is the number of the last chiral carbon in the molecule? Is it an L or D sugar?

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  • Haworth Structures: Instruction
    • Convert between open-chain structures of carbohydrates and Haworth projections.
    • Every monosaccharide exists in a dynamic equilibrium between its linear and cyclic forms, with the cyclic form being strongly favored.
    • Monosaccharides retain their identity regardless of their form.

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  • Haworth Structures: Instruction (continued)
    • Monosaccharides like glucose can form rings (cyclic compounds).

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  • Glycosidic Linkages
    • Glycosidic linkages are the connections made by an ether group to bind two ringed sugars into a single compound.
    • At least one side of the ether is connected to an anomeric carbon.
    • The anomeric carbon is the carbon in a sugar ring that is connected to two oxygen atoms because it was the carbonyl carbon in the linear sugar.
    • The anomeric carbon can have two different arrangements of the hydroxyl group.

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  • Glycosidic Linkages (continued)
    • Bonds only break and form at the anomeric carbon.
    • Rotation in the open chain allows for 2 orientations of the hydroxyl group and hydrogen at the anomeric carbon when in the cyclic form.
    • Carbonyl rotated upward when the ring closes creates one form, while downward creates another.

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  • Haworth Structures
    • Haworth structures are 2D representations of the 3D arrangement of atoms in cyclic sugars.
    • The anomeric carbon is drawn as carbon on the right side.
    • The molecule is arranged as if the Fischer projection was tipped on its side.
    • Wedge bonds indicate carbons in front; line bonds indicate carbons in back.
    • In glucose, groups on carbon 5 are rotated so that the –OH points toward the anomeric carbon, creating the ether group.

Page 38

  • Haworth Structure Example
    • Represents how the conversion looks between open-chain and Haworth projections.

Page 39

  • Haworth Structures: Practice
    • Question: Use the Fischer projection below to draw the Haworth structure of β-glucose.

Page 40

  • Carbohydrate Chemistry Assignment
    • Oxidation and Reduction Reactions of Carbohydrates

Page 41

  • Carbohydrate Redox: Instruction
    • A sugar acid is made when the carbonyl group of a monosaccharide is oxidized by an oxidizing agent.
    • Aldoses are oxidized to carboxylic acids.
    • Ketoses are ONLY oxidized after they interconvert to aldoses in the presence of a base.

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  • Carbohydrate Redox: Instruction (continued)
    • A sugar alcohol is made when the carbonyl carbon is reduced to a primary or secondary alcohol by catalytic hydrogenation.
    • Produced by aldehyde reductase enzymes in the body.
    • Renamed by replacing –ose with –itol suffix.

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  • Reducing Sugars
    • Reducing sugars are any sugars that can be oxidized.
    • They are identified through reactions with Tollen’s reagent (where blue solution turns red) or Benedict’s reagent (where blue solution turns brick red).
    • Monosaccharides are always reducing sugars, while disaccharides can also be reducing sugars.

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  • Non-reducing Sugars
    • Disaccharides are not reducing sugars if the glycosidic linkage connects the anomeric carbons.
    • Example: Sucrose, a disaccharide, is not a reducing sugar due to both anomeric carbons being involved in the glycosidic bond.

Page 45

  • Glycosidic Linkages: Instruction
    • Identify glycosidic bonds and remember that glycosidic linkages bind two ringed sugars into a single compound.
    • At least one side of the ether is connected to an anomeric carbon.

Page 46

  • Alpha and Beta Sugars
    • Alpha sugar: Hydroxyl group is below the anomeric carbon.
    • Beta sugar: Hydroxyl group is above the anomeric carbon.
    • Carbon 1 is defined as the anomeric carbon.

Page 47

  • Formation of Glycosidic Linkages
    • Glycosidic linkages are formed by condensation reactions in which the hydroxyl group of one monosaccharide combines with hydrogen of another monosaccharide, releasing water.
    • This process joins monosaccharides together to form disaccharides or polysaccharides.

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  • Disaccharides
    • Formed when two monosaccharides are joined by a condensation reaction that creates a glycosidic linkage.
    • Can be hydrolyzed by acid or an appropriate enzyme.
    • Examples of common disaccharides include:
    • Lactose (galactose & glucose)
    • Sucrose (glucose & fructose)
    • Maltose (glucose & glucose)
    • Lactose and maltose are reducing sugars, but sucrose is not (due to both anomeric carbons being involved in the glycosidic bond).

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  • Formation of Sucrose
    • “Table Sugar” is pure sucrose, which is a disaccharide that hydrolyzes to glucose and fructose.
    • Formed by an α 1,2’-glycosidic bond, made of a glucose and fructose.

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  • Equatorial Bonds and Beta Linkages
    • Equatorial bonds are formed in beta linkages.

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  • Axial Bonds and Alpha Linkages
    • Axial bonds form alpha linkages, playing a crucial role in sugar structure.

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  • Polysaccharides
    • Polysaccharides are long chains of monosaccharides joined by glycosidic linkages.
    • They can be branched or unbranched and consist of multiple types of monosaccharides.
    • Polysaccharides release monosaccharides by hydrolysis using an acid or the proper enzyme.
    • Function as energy storage molecules or structural molecules.
    • Examples include: Starch, glycogen, cellulose, chitin.

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  • Storage Polysaccharides
    • Storage polysaccharides are used to store energy and are synthesized or metabolized based on the monosaccharide levels in an organism.

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  • Function of Structural Polysaccharides
    • Structural polysaccharides provide rigidity to organisms and are not used for energy; they are difficult for predators to metabolize.

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  • Glycogen
    • Glycogen is a highly branched molecule that is stored in liver and muscle cells in humans.
    • Made of glucose and employs α 1-6 linkages at branch points and α 1-4 linkages in straight chains.

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  • Starch
    • Starch is a storage polysaccharide made from glucose, composed of a mixture of amylose (unbranched, using α 1-4 linkages) and amylopectin (branched, with α 1-6 linkages at branch points and α 1-4 linkages in straight chains).

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  • Cellulose
    • Cellulose is a structural polysaccharide providing structural support to plant cell walls and helping organisms maintain their shape.
    • Composed of glucose and features unbranched β 1-4 linkages between glucose monomers, creating tightly packed, long chains that lend rigidity and tensile strength.
    • Many herbivores rely on bacteria and protists to produce the cellulase enzyme needed to digest cellulose.

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  • Structure of Cellulose (continued)
    • Unbranched with β 1-4 linkages between glucose monomers adds to its structural stability.

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  • Chitin
    • Chitin is a structural polysaccharide forming fungal cell walls and the exoskeleton of various arthropods.
    • Made of repeating N-acetyl-β-d-glucosamine monomers, with unbranched β 1-4 linkages between glucosamine monomers, providing rigidity to organisms.

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  • Biological Importance of Glucose and Glycogen
    • Glucose molecules are broken down to create energy, whereas glycogen molecules serve to store energy in the form of glucose.

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  • Digestibility of Glycogen vs. Cellulose
    • Humans can metabolize glycogen due to alpha linkages; however, cellulose contains beta linkages which humans cannot digest.