GOB Chemistry Study Notes: Organic Compounds, Chemical Reactions, Carbohydrates, and Gas Laws

Chapter 4: Introduction to Organic Compounds

Representations of Molecules

Organic molecules can be represented in several ways, each providing different levels of structural detail.

• Molecular Formula: Shows the number and type of atoms (e.g., C2H6).

• Condensed Formula: Groups atoms to show connectivity (e.g., CH3CH3).

• Lewis/Expanded Formula: Shows all atoms and bonds, including lone pairs.

• Skeletal Formula: Simplifies carbon backbone; vertices represent carbon atoms, hydrogens often omitted.

Example: Ethanol can be written as C2H6O (molecular), CH3CH2OH (condensed), or as a skeletal structure.

Functional Group Identification

Functional groups are specific atom arrangements that define chemical properties.

• Alcohol: –OH group

• Alkyl Halide: –X (X = Cl, Br, etc.)

• Ketone: C=O within carbon chain

• Carboxylic Acid: –COOH

• Aldehyde: C=O at end of chain

Example: Acetone is a ketone; ethanol is an alcohol.

IUPAC Naming of Organic Compounds

The International Union of Pure and Applied Chemistry (IUPAC) system provides rules for naming organic molecules.

• Alkanes: Saturated hydrocarbons (single bonds), e.g., methane, ethane.

• Alkenes: Contain double bonds, e.g., ethene.

• Alkynes: Contain triple bonds, e.g., ethyne.

• Alcohols: Named with suffix "-ol" (e.g., ethanol).

• Alkyl Halides: Prefixes like chloro-, bromo- (e.g., chloromethane).

• Ketones: Suffix "-one" (e.g., propanone).

• Carboxylic Acids: Suffix "-oic acid" (e.g., ethanoic acid).

• Aldehydes: Suffix "-al" (e.g., ethanal).

Bond Length vs. Bond Strength

Bond length and strength are inversely related; shorter bonds are stronger.

• Single bonds: Longest and weakest

• Double bonds: Intermediate

• Triple bonds: Shortest and strongest

Alkyl and Halogen Substituent Naming

Substituents are named as prefixes in IUPAC nomenclature.

• Alkyl: methyl, ethyl, propyl, etc.

• Halogen: chloro-, bromo-, fluoro-, iodo-

Isomers

Isomers are compounds with the same formula but different structures.

• Structural Isomers: Differ in connectivity.

• Stereoisomers: Same connectivity, different spatial arrangement.

Stereoisomers: Cis/Trans and Chiral Molecules

Stereoisomers include cis/trans and chiral molecules.

• Cis/Trans Isomers: Occur in double bonds and cyclic structures; cis = same side, trans = opposite sides.

• Chiral Molecules: Have a chiral center (carbon with four different groups); non-superimposable mirror images.

Example: 2-butene has cis and trans forms.

Enantiomers

Enantiomers are pairs of chiral molecules that are mirror images.

• Properties: Identical physical properties except for optical activity.

Fatty Acid Designations

Fatty acids are classified by omega and X:X designations.

• Omega: Position of first double bond from methyl end (e.g., omega-3).

• X:X: Number of carbons:number of double bonds (e.g., 18:1).

• Saturated: No double bonds

• Monounsaturated: One double bond

• Polyunsaturated: Multiple double bonds

Extra Credit Functional Groups

• Thiols: –SH group

• Sulfides: R–S–R'

• Disulfides: R–S–S–R'

• Phenols: Aromatic ring with –OH

Chapter 5: Chemical Reactions

Enthalpy (ΔH) and Free Energy (ΔG)

Thermodynamics describes energy changes in reactions.

• Enthalpy (ΔH): Heat change; exothermic (ΔH < 0), endothermic (ΔH > 0).

• Free Energy (ΔG): Determines spontaneity; exergonic (ΔG < 0, spontaneous), endergonic (ΔG > 0, non-spontaneous).

Equation:

$\Delta G = \Delta H - T \Delta S$

Increasing Reaction Rate

• Temperature: Higher temperature increases rate.

• Reagents: Higher concentration increases rate.

• Catalyst: Lowers activation energy, increases rate.

Categories of Organic Reactions

• Synthesis: Two or more reactants form one product.

• Decomposition: One reactant breaks into two or more products.

• Exchange/Displacement: Parts of molecules are exchanged.

Specific Types of Reactions

• Redox (Inorganic and Organic): Electron transfer; oxidation (loss), reduction (gain).

• Combustion: Reaction with O2 producing CO2 and H2O.

• Addition Reactions: Atoms added to double/triple bonds.

• Hydration: Addition of water to alkenes.

• Hydrogenation: Addition of H2 to alkenes/alkynes.

• Condensation: Two molecules join, releasing water.

• Hydrolysis: Water splits a molecule.

Example: Hydration of ethene forms ethanol.

Chapter 6: Carbohydrates - Life's Sweet Molecules

Types of Saccharides

Carbohydrates are classified by the number of sugar units.

• Monosaccharides: Single sugar units (e.g., glucose).

• Disaccharides: Two monosaccharides joined (e.g., sucrose).

• Oligosaccharides: Few (3-10) sugar units.

• Polysaccharides: Many sugar units (e.g., starch, cellulose).

Alcohol Classification in Carbohydrates

• Primary Alcohol: –OH on carbon attached to one other carbon.

• Secondary Alcohol: –OH on carbon attached to two other carbons.

• Tertiary Alcohol: –OH on carbon attached to three other carbons.

Monosaccharide Classification

• Triose: 3 carbons

• Tetrose: 4 carbons

• Pentose: 5 carbons

• Hexose: 6 carbons

Aldose vs. Ketose

• Aldose: Aldehyde group at C1 (e.g., glucose).

• Ketose: Ketone group at C2 (e.g., fructose).

Stereoisomers in Monosaccharides

The number of stereoisomers is determined by chiral centers.

• Formula: $2^n$ where n = number of chiral centers.

• Diastereomers: Stereoisomers not mirror images.

• Enantiomers: Mirror image stereoisomers.

• Epimers: Differ at only one chiral center.

Oxidation and Reduction of Aldose

• Oxidation: Aldose forms carboxylic acid.

• Reduction: Aldose forms alcohol.

Anomeric Carbon and Cyclic Forms

Monosaccharides cyclize to form hemiacetals.

• Anomeric Carbon: C1 in aldose; forms bond with –OH.

• Beta: –OH up

• Alpha: –OH down

Reducing Sugars

Reducing sugars have free anomeric carbon; can reduce other compounds.

• Monosaccharides: All are reducing.

• Disaccharides: Reducing if anomeric carbon is free.

Formation of Disaccharides

Two monosaccharides join via condensation, forming glycosidic bonds.

• Alpha or Beta: Depends on orientation of –OH.

• Numbering: Indicates which carbons are linked (e.g., 1→4).

Extra Credit: Fischer and Haworth Projections

• Fischer Projection: Linear representation.

• Haworth Projection: Cyclic form.

• Conversion: Shows cyclization and orientation of –OH.

Polysaccharides: Storage and Structure

• Starch: Plant storage; amylose (linear), amylopectin (branched).

• Glycogen: Animal storage; highly branched.

• Cellulose: Structural; linear, β(1→4) linkages.

• Chitin: Structural; similar to cellulose, contains nitrogen.

Bonding and Structure of Polysaccharides

Polysaccharide	Bond Type	Function
Amylose	α(1→4)	Plant storage
Amylopectin	α(1→4), α(1→6)	Plant storage (branched)
Cellulose	β(1→4)	Plant structure
Chitin	β(1→4) (with N-acetyl group)	Animal structure
Glycogen	α(1→4), α(1→6)	Animal storage (highly branched)

Starch: Plant Glucose Storage

• Amylose: Linear polymer

• Amylopectin: Branched polymer

ABO Blood Typing and Oligosaccharides

• Universal Donor: Type O

• Universal Acceptor: Type AB

• Oligosaccharides: Determine blood type

Heparin

• Definition: Anticoagulant polysaccharide

• Function: Prevents blood clotting

Chapter 7.1: States of Matter and Their Attractive Forces (Gas Laws)

Pressure Unit Conversion

Pressure can be measured in several units; conversion factors are essential.

• Common Units: atm, mmHg (torr), Pa, psi

• Example: 1 atm = 760 mmHg = 101,325 Pa

Boyle's Law (Conceptual)

Boyle's Law describes the relationship between pressure and volume at constant temperature.

• Statement: As volume decreases, pressure increases (inverse relationship).

• Equation:

$P_1 V_1 = P_2 V_2$

Charles' Law (Conceptual)

Charles' Law relates volume and temperature at constant pressure.

• Statement: As temperature increases, volume increases (direct relationship).

• Equation:

$\frac{V_1}{T_1} = \frac{V_2}{T_2}$

Gay-Lussac's Law (Conceptual)

Gay-Lussac's Law relates pressure and temperature at constant volume.

• Statement: As temperature increases, pressure increases (direct relationship).

• Equation:

$\frac{P_1}{T_1} = \frac{P_2}{T_2}$

Extra Credit: Calculations Using Gas Laws

Use provided formulas to solve for unknowns in gas law problems.

• Boyle's Law: Solve for P or V given other values.

• Charles' Law: Solve for V or T.

• Gay-Lussac's Law: Solve for P or T.

Example: If a gas at 1 atm and 2 L is compressed to 1 L, the new pressure is 2 atm (Boyle's Law).

Additional info: Academic context and examples were added to clarify brief points and ensure completeness.