Russia 10 класс Chemistry (advanced)
Chapters: 5
1. Foundations of organic chemistry
Carbon atom and hybridisation · Structure theory and isomerism · Reaction mechanisms
- Valence Bond Theory and Hybridisation – Valence bond theory says a covalent bond forms when half-filled orbitals of two atoms overlap and the two electrons pair up with opposite spins. Head-on overlap makes a strong σ (sigma) bond; side-on overlap of p orbitals makes a weaker π (pi) bond. To explain real shapes, an atom first mixes its orbitals into equal hybrid orbitals: sp (linear, 180°), sp² (trigonal planar, 120°), sp³ (tetrahedral, 109.5°), sp³d (trigonal bipyramidal) and sp³d² (octahedral).
- IUPAC Nomenclature and Isomerism of Organic Compounds – Millions of organic compounds exist, so every one needs a clear, unique name. The IUPAC system builds a name from three parts: the word root (number of carbons in the main chain), the suffix (type of bond and main functional group) and the prefixes (side groups). You pick the longest chain that holds the main group, number it so the main group and branches get the lowest numbers, and write side groups in alphabetical order. Isomers are compounds with the same molecular formula but different arrangement. Structural isomers differ in how atoms are joined (chain, position, functional group, metamerism). Stereoisomers are joined the same way but differ in 3D arrangement (geometrical cis/trans and optical isomers).
- Basics of Organic Reaction Mechanism – A reaction mechanism is the step-by-step story of which bonds break, which form, and where the electrons move. A covalent bond can break in two ways. In homolysis each atom takes one electron and free radicals form. In heterolysis one atom takes both electrons, giving a carbocation (C with + charge) and a carbanion or an anion. Electron-poor species that seek electrons are electrophiles; electron-rich species that give electrons are nucleophiles. The movement of electrons inside a molecule is controlled by four effects: the inductive effect (pull along σ bonds), the resonance effect (spreading of π electrons), the electromeric effect (a temporary full shift when a reagent attacks) and hyperconjugation (σ C–H electrons spreading into a nearby empty p orbital or π bond). These effects decide how stable an intermediate is and where a reagent attacks.
2. Hydrocarbons
Alkanes and cycloalkanes · Alkenes · Dienes · Alkynes · Arenes · Halogen derivatives · Hydrocarbon sources
- Alkanes – Alkanes are hydrocarbons with only single C–C bonds. Their general formula is CnH2n+2. We make them by adding hydrogen to alkenes, by the Wurtz reaction, by reducing alkyl halides and by decarboxylation. They are non-polar, burn with a lot of heat and swap H for Cl in light. Around the C–C bond the molecule can twist into staggered and eclipsed shapes called conformations.
- Alkenes – Alkenes are hydrocarbons with one C=C double bond and the formula CnH2n. The double bond is one σ bond plus one π bond, so the molecule is flat around it and cannot twist. That gives cis and trans isomers. We make alkenes by removing small molecules (H₂O, HX, X₂) or by partly adding H₂ to alkynes. Alkenes mainly do addition reactions: H₂, X₂, HX (Markovnikov rule, or anti-Markovnikov with peroxide), water, ozone, KMnO₄ and polymerisation.
- Alkynes – Alkynes have a C≡C triple bond and the formula CnH2n−2. The two triple-bond carbons are sp hybridised, so the molecule is a straight line. A hydrogen on a triple-bond carbon is weakly acidic because an sp carbon holds electrons tightly: strong bases like NaNH₂ remove it. The triple bond can open twice, so alkynes add two molecules of H₂, X₂ or HX. With water (Hg²⁺ catalyst) they give aldehydes or ketones, and three ethyne molecules can join into benzene.
- Benzene and Aromaticity – Benzene (C₆H₆) is a flat ring of six sp² carbons. Its six π electrons are spread over the whole ring, so all C–C bonds are equal and the ring is extra stable. A ring like this is called aromatic when it is cyclic, planar, fully conjugated and has 4n + 2 π electrons (Hückel rule). Benzene prefers electrophilic substitution (nitration, halogenation, sulphonation, Friedel–Crafts) over addition, because substitution keeps the stable ring. A group already on the ring decides where the next group goes: ortho/para or meta. Benzene and fused-ring hydrocarbons are toxic and can cause cancer.
- Haloalkanes – A haloalkane is an alkane in which a hydrogen is replaced by a halogen (R–X). The C–X bond is polar: carbon is slightly positive, so nucleophiles attack it. Haloalkanes react by SN2 (one step, backside attack, inversion; best for 1°), SN1 (two steps, flat carbocation, racemic product; best for 3°) or elimination (strong base in alcohol gives an alkene).
3. Oxygen-containing compounds
Alcohols and ethers · Phenol · Aldehydes and ketones · Carboxylic acids and derivatives · Carbohydrates
- Alcohols – An alcohol is a carbon compound with an –OH group on an sp³ carbon (R–OH). Count the carbons joined to the C–OH carbon to classify it as primary (1°), secondary (2°) or tertiary (3°). Name it as alkan-n-ol, giving –OH the lowest number. Make alcohols from alkenes (acid-catalysed hydration or hydroboration–oxidation), by reducing aldehydes, ketones and acids, or from Grignard reagents. H-bonding gives them high boiling points and water solubility. Reactions break either the O–H bond (acidic: Na, esterification) or the C–O bond (HX, dehydration), and 1°/2° alcohols can be oxidised. Methanol and ethanol are the key commercial alcohols.
- Phenols – A phenol has –OH joined straight to a benzene ring carbon. It is made from chlorobenzene (NaOH, 623 K, 300 atm), benzenesulphonic acid, diazonium salts or cumene. Phenol is more acidic than alcohols and water because the phenoxide ion spreads its negative charge over the ring; electron-pulling groups like –NO₂ (at ortho/para) raise acidity, electron-pushing groups like –CH₃ lower it. The –OH group activates the ring at ortho and para positions: bromine water gives 2,4,6-tribromophenol, dilute HNO₃ gives o- and p-nitrophenol, NaOH + CO₂ gives salicylic acid (Kolbe) and CHCl₃ + NaOH gives salicylaldehyde (Reimer–Tiemann).
- Aldehydes and Ketones: Structure, Preparation and Reactions – Aldehydes and ketones both have a carbonyl group, C=O. In an aldehyde the carbonyl carbon has at least one H on it (−CHO). In a ketone it has two carbon groups (−CO−). The C=O bond is polar: carbon is slightly positive, oxygen slightly negative. So electron-rich particles (nucleophiles) attack the carbon. This one idea explains most of their reactions: addition of HCN, NaHSO₃, alcohols and ammonia derivatives. Aldehydes are easy to oxidise (Tollens and Fehling tests), ketones are not. A hydrogen on the carbon next to C=O (α-H) is slightly acidic, which gives aldol condensation. Aldehydes with no α-H give the Cannizzaro reaction instead.
- Carboxylic Acids: Carboxyl Group, Acidity and Reactions – A carboxylic acid has the carboxyl group, −COOH: a C=O and an O−H on the same carbon. It can give away H⁺, and the ion left behind (carboxylate, −COO⁻) is stable because its negative charge is shared equally by two oxygen atoms. That is why these acids are stronger than phenols and alcohols (but weaker than mineral acids like HCl). Groups that pull electrons (Cl, F, NO₂) make the acid stronger; groups that push electrons (alkyl) make it weaker. We make carboxylic acids by oxidising alcohols, aldehydes or alkylbenzenes, by hydrolysing nitriles, esters and amides, or from Grignard reagents and CO₂. Their key reactions: salt formation with NaHCO₃ (CO₂ fizz), esterification, acid chloride and anhydride formation, reduction to alcohols, decarboxylation and the HVZ reaction.
- Carbohydrates: Classification, Glucose, Disaccharides and Polysaccharides – Carbohydrates are sugars and the big molecules made from sugars. Chemically they are polyhydroxy aldehydes or ketones (many –OH groups plus one C=O), or things that give these on hydrolysis. We sort them by how many sugar units they have: one (monosaccharide), two to ten (oligosaccharide) or many (polysaccharide). Glucose is an aldose with six carbons; fructose is a ketose. Two units join by a glycosidic (–O–) bond to give disaccharides like sucrose, maltose and lactose. Hundreds join to give starch, cellulose and glycogen.
4. Nitrogen-containing compounds
Amines and aniline · Amino acids and proteins · Heterocycles and nucleic acids
- Amines: Structure, Naming, Preparation, Basicity and Reactions – An amine is ammonia with one, two or three H atoms swapped for carbon groups. The N keeps a lone pair, so amines are bases and nucleophiles. Count the C atoms on N to get 1°, 2° or 3°. Make them by reducing nitro compounds, nitriles or amides, from alkyl halides + NH₃, by Gabriel (1° only) or Hofmann bromamide (one C fewer). Alkyl groups push electrons and raise basicity; the ring in aniline pulls the pair away and lowers it. Key reactions: salts with acids, acylation, carbylamine test (1°), Hinsberg test (1°/2°/3°), nitrous acid and ring substitution in aniline.
- Proteins and Enzymes: Amino Acids, Peptide Bond, Structure and Denaturation – Proteins are long chains of amino acids. Each amino acid has an amino group (–NH₂), an acid group (–COOH), a hydrogen and a side group R on one carbon. The –COOH of one amino acid joins the –NH₂ of the next, losing water, to make a peptide bond (–CO–NH–). The order of amino acids is the primary structure; coils and sheets are the secondary structure; the full 3D fold is the tertiary structure; several chains together make the quaternary structure. Heat, acid or alcohol can undo the folds (denaturation). Enzymes are mostly proteins that speed up reactions in the body.
- Vitamins, Nucleic Acids and Hormones: Types, Roles, DNA and RNA – Vitamins are small organic compounds we need in tiny amounts from food; A, D, E, K dissolve in fat and B, C dissolve in water, and a lack of each causes a known disease. Nucleic acids (DNA and RNA) are long chains of nucleotides. Each nucleotide = a pentose sugar + a phosphate + a nitrogen base. DNA has deoxyribose, bases A, G, C, T and two strands in a double helix, where A pairs with T and G with C. RNA has ribose, U instead of T and usually one strand. Hormones are chemical messengers made by glands, and can be steroids, proteins/peptides or amino acid derivatives.
5. Polymers
Polymer materials
- Polymers – A polymer is a giant molecule made by joining many small molecules (monomers) into a long chain. In addition polymerisation, monomers with a C=C double bond open up and link with nothing lost (ethene → poly(ethene)). In condensation polymerisation, two kinds of monomer with reactive groups at both ends join and give off a small molecule such as water at every link (nylon, polyester). Nature makes polymers too: starch, cellulose, proteins, DNA, rubber. Separate chains give thermoplastics that melt and can be recycled; cross-linked chains give thermosets that never melt. Most plastics do not rot, so we must reduce, reuse and recycle them.