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NCSU CH 221 - Exam 1 Study Guide

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CH 221 Edition 7Exam # 1 Study Guide Lectures: 1 - 12Lecture 1 (January 7)Organic Chemistry - Organic compounds form the basis of life on Earth- Organic Com pounds- compounds that contain carbon- Functional Groups- used to classify organic compounds based on their chemical structuresLecture 2 (January 9th) Electric Structure and Bonding - Atoms are composed of - Protons (positive charge)- Neutrons (neutral charge)- Electrons (negative charge- Isotopes of carbon have some atomic number but contain different numbers of neutrons- Carbon can share 4 valence electrons in 4 covalent bonds- Four different kinds of orbitals denoted as; s p d f- s orbitals- spherical, nucleus at center- p orbitals- dumbbell shaped, nucleus in the middle of lobes- First shell is closest to the nucleus- The closer the atomic orbital is to the nucleus, the lower the energy- Within a shell, s < p, meaning s is lower energy than p- Aufbau Principle- an electron will go into the atomic orbital at the lowest energy- Pauli Exclusion Principle- no more than two electrons can inhabit an orbital- Hund’s Rule- an electron will go to an empty orbital before pairing up with other electrons- Atoms to the left of carbon give up electrons- Atoms to the right of carbon accept electrons- Octet RuleAn octet means having 8 valence electrons. This is associated with the stability of the noble gases. Atoms form octets to become more stable by losing, gaining, or sharing electrons in ionic or covalent bonds- Hydrogen ExceptionHydrogen is content with only 2 valence electrons and can either lose or gain an electronin order to complete an octet.- Ionic bonding is between ions of opposite charges (ex NaCl)- Covalent bonds are formed by sharing electrons- Nonpolar covalent bonds mean bonded atoms are the same- Polar covalent bonds mean bonded atoms are differentLecture 3 (January 12th)Electric Structure and Bonding Part 2- The number of bonds plus the number of lone pairs must equal 4- Neutral carbons form four bonds- If carbon does not form four bonds, it becomes charged- Formal charge is calculated by the number of valence electrons – ½ the number of bonding electronsORThe number of valence electrons – the number of bonds- Neutral Nitrogen forms three bonds and has one lone pair.- Oxygen has two bonds and two lone pairs, like in waterThe steps to drawing Lewis structures for these compounds are:1. Count total number of electrons2. Draw individual atoms including their valence electrons3. Pair atoms around carbon chain- Sigma and Pi bonds help form the bonds between carbons and hydrogens- Sigma bonds are very strong therefore require a huge amount of energy to be broken (dissociated).- Carbon must promote an electron in order to have four bonds meaning one electron from the 1s energy level jumps to the unfilled 2p energy levelLecture 4 (January 14th)More on Bonding and the Beginning of Acids and Bases- Single bond= 1 sigma Double bond= 1 sigma, 1 pi Triple bond= 1 sigma, 2 pi- Ammonia (NH3) – Four orbitals are hybridized forming four sp3 hybrid orbitals. Lone pair electrons are in an sp3 orbital. - Water (H2O) – Similar to NH3 except it has two orbitals that each contain a lone pair and two orbitals used to form bonds.- Bond strength increases as bond length decreases- The carbon to carbon triple bond is the strongest bond with the shortest length.- Electronegativity increase to the right, and up the periodic table. It is the measure of how much an atom attracts electrons.- An acid loses a proton, and a base gains it.- Acid/base reactions are reversible meaning they are considered equilibrium reactions. - When an acid loses a proton, it forms a conjugate base and when a base gains a proton, it forms a conjugate acid. - The stronger the acid, the weaker the conjugate base.- pKa= -logKapKa < 1 very strong acidpKa= 1-3 moderately strong acidpKa= 3-5 weak acidpKa= 5-15 very weak acidpKa > 15 extremely weak acidLecture 5 (January 16th)More on Acids and Bases- pH= -log[+¿H¿] indicates that the concentration of protons in a solution pH= -log[+¿H3O¿].- Protonated alcohols and carboxylic acids are much more acidic than their counterparts- Alcohols can behave as either an acid or base. - The curved arrows in some reactions point from the electron donor to the electron acceptor. - A carboxylic acid also acts as both an acid and a base and has reactions very similar to those of alcohols.- Lewis definitionsAcids- the species that accepts a share in an electron pairBases- the species that donates a share in an electron pair. - All Bronsted acids are Lewis acids and all Bronsted bases are Lewis bases. An amine can behave as either an acid or a base much like alcohols and carboxylic acids. - In reactions, the stronger acid behaves as the acid- Equilibrium favors the formation of weaker acids. - Electronegativity has an effect on the pKa values which in turn effects the pH- When atoms are the same size, the strongest acid has its hydrogen attached to the most electronegative atom. - Alcohols are stronger acids than amines because oxygen is more electronegative than nitrogen.Lecture 6 (January 21st)The End of Acids and Bases and the Beginning of Organic Nomenclature- A carboxylic acid is neutral in its acidic form (RCOOH) and charged in its basic form (−¿RCOO¿).- An amine is charged in its acidic form and neutral in its basic form.- The formula pKa= pH + log −¿A¿¿[HA ]¿ tells us whether a compound will be acidic (with a proton) or basic (without a proton). - The general molecular formula of the hydrocarbon group Alkanes is CnH2 n+2- The name of the compound is directly related to the number of carbons present.1= meth 2= eth 3= prop 4= but 5= pent 6= hex7= hept 8= oct 9= non 10= dec 11= undec 12= dodec13= tridec 20= eicos 21= heneicos 30= triacont- Homologous compounds differ only by the addition or subtraction of a CH3 group.- There are constitutional isomers that have the same molecular formula but the atoms are linked differently. Lecture 7 (January 23rd)The Rules of Naming Organic Hydrocarbons- First identify the longest continuous chain also known as the parent hydrocarbon. Always identify the parent hydrocarbon then number accordingly. Add the name of the substituent then number the chain in the direction that gives the substituent as low a number as possible.- Common vs Systematic nomenclature simply means some compounds are better known by easier to say names than their systematic name may be.- The common name


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