Organic and Nuclear Chemistry Review

Organic Chemistry Basics and Historical Context

• Definition of Organic Chemistry: The study of all carbon-containing things. Organic chemistry is the foundational science for biology and spans various industrial fields.
• Historical Timeline: Organic chemistry emerged as a distinct field in the 1700s/18th century.
• Friedrich Wöhler:
  • He was the first person to synthesize an organic compound from scratch.
  • Previously, it was believed organic compounds could only be produced by living systems (a "vital force" theory).
  • He synthesized urea, which the human body produces in urine.
  • Wöhler is also credited with inventing graduate school because he was the first to have students assist him with his research.
• Major Elements in Organic Molecules:
  • Carbon: The central element and "star" of organic chemistry.
  • Hydrogen: Frequently bound to carbon.
  • Oxygen and Nitrogen: Common additions to organic structures.
  • Halogens: Chlorine ($Cl$), Fluorine ($F$), Bromine ($Br$), and Iodine ($I$).

Functional Groups and Core Building Blocks

• Definition: Building blocks within molecules that determine their reactivity and structure, similar to "chemical LEGOs."
• Alkanes: Organic molecules containing only carbons and hydrogens with all single bonds. These are considered saturated (containing the maximum amount of hydrogen).
• Alkenes: Hydrocarbons that contain at least one double bond.
• Alkynes: Hydrocarbons that contain at least one triple bond.
• Amines: Functional groups containing a Nitrogen ($N$) atom.
• Alcohols: Contain Hydroxyl groups ($OH$). The name usually ends in "-ol."
• Ethers: An oxygen atom covalently bound between two carbon atoms ($C-O-C$).
• Thiols: Smelly compounds containing a sulfur atom ($S$).
• Carbonyl Groups ($C=O$): A carbon double-bonded to an oxygen. Varieties include:
  • Aldehydes: The carbonyl carbon is bonded to at least one Hydrogen.
  • Ketone: The carbonyl carbon is sandwiched between two other carbons.
  • Esters: A carbonyl carbon bonded to an oxygen, which is then bound to more carbons.
  • Carboxylic Acid: A carbonyl carbon bonded to an $OH$ group.
  • Amide: A carbonyl carbon bonded to a Nitrogen atom.

Molecular Representations and Drawing Styles

• Lewis Structures: Show explicit connectivity where single lines represent shared electron pairs between specific atoms.
• Ball-and-Stick Models: Represent molecular shape. Notably, carbon chains are not straight lines but exist in a zigzag shape due to tetrahedral bonding angles.
• Space-Filling Models: Represent the volume of atoms like balloons stuck together; realistic for size but difficult for seeing internal shape or bonding.
• Expanded Form: Every single bond is explicitly drawn out.
• Condensed Form: Shows explicit carbon-carbon bonds, but lists the number of hydrogens attached to each carbon as a subscript (e.g., $CH_3-CH_2-CH_3$). Every carbon must have exactly four bonds.
• Skeletal Structure (Zigzag Structure):
  • Most efficient way to draw molecules.
  • Carbon atoms are assumed to be at every end of a line and every vertex (point where direction changes).
  • Hydrogens are not explicitly drawn; they are assumed to be present in whatever amount is necessary to give each carbon four bonds.
  • Drawing Rules: Extra bonds on "peaks" go up; extra bonds on "valleys" go down.

IUPAC Naming Conventions for Alkanes

• Parent Chain: The longest continuous chain of carbons determines the base name.
• Prefixes for Carbon Counts:
  • $1$: Meth-
  • $2$: Eth-
  • $3$: Pro-
  • $4$: But-
  • $5$: Pent-
  • $6$: Hex-
  • $7$: Hept-
  • $8$: Oct-
  • $9$: Non-
  • $10$: Dec-
• Substituents: Branches attached to the main chain, treated like "charms on a bracelet." Their suffix is changed from "-ane" to "-yl" (e.g., a one-carbon branch is a methyl group).
• Complex Substituents:
  • n-Propyl: A 3-carbon chain attached at the end carbon.
  • Isopropyl: A 3-carbon chain attached at the middle carbon.
  • n-Butyl: A 4-carbon chain attached via the end carbon.
  • sec-Butyl: A 4-carbon chain attached via the second carbon.
  • Isobutyl: A 4-carbon chain arranged in a T-shape.
  • tert-Butyl: A 4-carbon chain arranged in a cross shape.
• Numbering: The parent chain must be numbered starting from the end closest to the substituents to give the branches the lowest possible location numbers.
• Redundancy: If multiple identical substituents exist, prefixes like di-, tri-, or tetra- are used, and every substituent must have a specific location number (e.g., $2,2,4\text{-trimethylpentane}$).

Properties and Reactions of Alkanes and Alkenes

• Alkane Reactions:
  • Combustion: Burning in the presence of Oxygen ($O_2$). Products are always Carbon Dioxide ($CO_2$) and Water ($H_2O$).
  • Substitution: A Hydrogen is swapped for a Halogen ($Cl_2$, $Br_2$, etc.). This requires high heat or light energy. Product is a haloalkane and an acid (e.g., $HCl$).
• Alkene/Alkyne Properties:
  • Geometric Isomers: Double bonds do not twist. This creates Cis (groups on the same side) and Trans (groups on opposite sides) molecules.
  • Addition Reactions: The double bond opens into a single bond to accommodate new atoms.
  • Hydrogenation/Halogenation: Adding $H_2$ or $Cl_2$ across the double bond.
  • Hydration: Adding Water ($H_2O$) to an alkene. One carbon gets a Hydrogen and the other gets an $OH$ group, creating an alcohol.

Notable Molecules and Historical Applications

• Tetrachloromethane ($CCl_4$):
  • Synthesized by Michael Faraday (who also invented the first Bunsen burner).
  • Initially used as a dry cleaning solvent, refrigerant, and fire extinguisher bulb (despite turning into poisonous phosgene gas when heated).
  • Once sold to women for menstrual pain and used as a dry shampoo (an alternative to the then-common use of gasoline on hair).
  • Currently known as a carcinogen that damages the central nervous system, kidneys, and liver.
• Ethylene: Produced by ripening fruit. Trapping it in a paper bag accelerates ripening.
• Aromatic Hydrocarbons: Cyclic molecules with alternating double/single bonds.
  • Xylene: Used in specimen slide prep.
  • Styrene: The monomer for Styrofoam.
• Phenol: A benzene ring with an alcohol group.
  • Joseph Lister used it as the first antiseptic after reading Louis Pasteur's Germ Theory.
  • Before antiseptics, $40-70 \%$ of patients died from infection after hospital amputations.
• Esters: Known for pleasant smells (Raspberries, Apples, Rum). Ethyl formate (an ester) was detected in the Milky Way galaxy.
• Amines and Amides:
  • Amines: Found in nicotine, heroin, codeine, and morphine.
  • Amides: Form the "peptide bonds" that hold amino acids together in proteins. Also used in Kevlar vests.
• Disulfide Bonds: Two sulfur atoms stuck together. They maintain hair texture; perms involve breaking and reforming these bonds using ammonium glycolate.

Introduction to Nuclear Chemistry

• Core Concept: Unlike general chemistry which focuses on electrons, nuclear chemistry focuses on the changes in the nucleus.
• Mass Defect: The mass of an atom is less than the sum of the masses of its individual protons and neutrons.
• Nuclear Binding Energy: The "missing mass" (mass defect) provides the energy to hold the nucleus together, calculated by $E = mc^2$.
  • $c$ (Speed of Light) $= 3 \times 10^8 \, \text{m/s}$.
  • Binding energies are extremely large, on the order of billions of $kJ \, mol^{-1}$.
• Notation: ${}^{A}_{Z}X$, where $A$ is the mass number (protons + neutrons) and $Z$ is the atomic number (protons).
• Band of Stability:
  • A specific ratio of neutrons to protons is required for a nucleus to be stable.
  • Lighter nuclei need a $1:1$ ratio; heavier nuclei require more neutrons to buffer proton repulsion.
  • Nuclei outside this "blue band" are radioactive and will spontaneously decay.

Radioactive Decay and Balancing Nuclear Equations

• Common Particles in Nuclear Reactions:
  • Alpha Particle ($\alpha$): Identical to a Helium nucleus (${}^{4}_{2}He$).
  • Beta Particle ($\beta$): A high-energy electron (${}^{0}_{-1}e$).
  • Gamma Ray ($\gamma$): Pure high-energy electromagnetic radiation (${}^{0}_{0}\gamma$).
  • Positron: A positive electron (${}^{0}_{+1}e$).
  • Neutron: ${}^{1}_{0}n$.
  • Proton: ${}^{1}_{1}H$ or ${}^{1}_{1}p$.
• Balancing Rules:
  • The sum of mass numbers (top) on the reactant side must equal the sum on the product side.
  • The sum of atomic numbers (bottom) must be equal on both sides.
• Parent and Daughter: The starting unstable isotope is the "parent"; the resulting products are "daughters."
• Decay Series: A sequence of decay events a nucleus undergo to reach a stable state (e.g., the Uranium-238 family). Many decay series end with Lead.

Questions & Discussion

• Q: Where was the video on Canvas?
• A: The professor admitted to a mistake, having forgotten to click the "publish" button on the module. The content was covered in person instead.
• Q: What math do we need for the final?
• A: The final will include big-picture take-home messages and review of integrated rate laws (kinetics), but no "hard" new math types. Two note cards are allowed for the final exam.
• Q: Is there a nuclear power plant in Washington?
• A: Students identified Hanford, though it is noted as being somewhat distant and currently focused on decommissioning/cleanup rather than active power generation.