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CHEM261 Midterm: chemistry Midterm 1

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David Clive

Chemistry 261 Final exam notes Methane (CH4) Ethane (C2C6). Propane(C3H8) Butane (C3H8) Single bond: Double bond: ethylene Ex: CO2 formal aldehyde: CH2O Acetic Acid: Triple Bond Acetylene: C2H2 Hydrogencyanide: Calculation for double bind equivalent: Ex: C3H6: N=9 Cyclohexane C6H12: Number of double bond equivale: 1= one ring, double bond 2=2 rings, 2 double bonds, 1 triple Dot structure “single bond” CH4: Double bond: C2H2 CH2O: Ionic Bond: Na --> e( Na ) Cl --> e( Cl ) Hybridization Atomic orbital: volume of space with high probability of finding an electron “1s,2s,2p, 3p,4s” Sp3 Hybridization Sp2 hybridization Sp hybridization Counting electron Formal charges: the hypothetical charge that would result if all bonding e- are shared equally. Formula: (#of ve in a free atom) – (# of be in bonded atom) Oxidation state: the hypothetical charge that would result if all binding e- are assigned. Formula: (# of be in a free atom) – (# of be in a bonded atom) Resonance structure Increase stability to delocalize, can't localize anion, decrease stability Resonance structure pattern Resonance structure of Benzene Resonance structure and hybridization Summary of hybridization 1) Sp: linear geometry 180, alkynes, at each triple Bond of c, 2s hybrid and 2p hybrid. 2) Sp2: trigonal planar 120, Allene, at each double Bond, 3s, 1p 3) Sp3: tetrahedral 109.5, alkanes, 4s Families of carbon compound Hydrocarbon: representing alkanes, alkenes, alkynes Alkanes: saturated, no multiple bond between c atoms (-ane) Alkenes: unsaturated, contain at least one c bond, (- ene) Alkynes: unsaturated, at least 1 triple bond, (-ynes) Aromatic compound: contain a special type of ring, the most common example is benzene ring. Unsaturated cyclic hydrocarbon known as aromatic compounds. This benzene compound is a six membered ring with alternating single and double bond called Kekule structure. (120) Benzene is a resonance hybrid of structure a and b Resonance stability Functional groups Common and specific arrangement of atoms that import predictable reactivity and properties to a molecule. Alkynes group: groups that would be obtain by removing a hydrogen atom from alkane. Alkane Alkyl Group Methane CH3-H Ethane CH3CH3-H Propane CH3CH2CH2-H Butane CH3CH2CH2CH2-H Propane can be derived into 2 groups. Removal of a group; removal of hydrogen from the middle carbon atom gives a group that is, isopropyl group. Removal of hydrogen from one of the end carbon gives a group that is, propyl group. Symbol R: is used to a general symbol to represent any alkyl group. Ex: R might be a methyl group, an ethyl group, propyl, isopropyl. Methyl Ethyl Propyl isopropyl Phenyl and benzyl group When a benzene ring is attached to some other group of atoms is a molecule, it is phenyl group. - The combination of a phenyl group and methylene group-C ( H2) is called benzyl group. (Phenyl group with benzyl ring) Alkyl halides or haloalkanes (haloalkanes) R-X Alkyl halides are compound in which a halogen atom ( fluorine, chlorine, bromine, iodine). Replaces a hydrogen atom of an alkane with a halogen. Ex: CH3Cl The generic formula for an alkyl halide is R-X where X is halogens and R is alkanes. Alkenyl Halide: a compound with a halogen atom bonded to an alkenes group carbon. An aryl halide: a halogen atom bonded to an aromatic ring such as benzene ring. Alcohol and phenols R-OH, -ol ending Methyl alcohol (methanol) has the structural formula CH3OH and is the simplest form of organic compound alcohols. • The characteristic functional group of this family is (-OH) group attached to an sp3 hybridized carbon atom. • As hydroxyl derivatives strives of alkenes: ethane molecules in which one hydrogen has been replaced by a hydroxyl group. • An alkyl dedicates of water: one hydrogen has been replaced by ethyl group. Three groups of alcohols: this classification is based on the degree of substitution of the carbon to which the hydroxyl group is directly attached. Primary alcohol: carbon has only one other carbon attached to it. Secondary alcohol: the carbon that bears the hydroxyl group also has 2 other carbon atoms attached. Tertiary alcohol: carbon atom bears the hydroxyl group has 3 other carbon attached to it. Phenol: a hydroxyl group is bonded to a benzene ring the combination of the ring and the hydroxyl Ethers: Ethers have general formula R-O-R or R’-O-R where R’ = alkyl or phenyl group. Ethers can be thoughts as derivatives of water in which both hydrogen atoms have been replaced by alkyl group. The bond angle at the oxygen atom of an ether is only slightly larger than the water. Naming ethers: name the 2 alkyl groups that attached to the oxygen atoms in an alphabetical orders, and add the word ether. If the 2 alkyl groups are he same, we used prefix (dimethylether)CH3CH2 –O– CH2CH3 Amines: May be considered as organic derivatives of ammonia This classification based on the number of organic groups that are attached to the nitrogen atoms. Note: Isopropylamine is a primary amine even though its Nh2 groups is attached to a secondary carbon atom. It is a primary amine because only one organic group is atatched to the nitrogen atom. • The nitrogen atom of an amine can be considered to be sp3 hybridized with the unshared electron pair occupying one orbital. Aldehydes and Ketones Aldehydes and ketones both contain the carbonyl group (C=O). Aldehydes: Ketones: the carbonyl group of ketone is bonded to 2 carbon atoms. Have a trigonal planar arrangement of groups around carbonyl atom. Carboxylic acids, esters and Amides A. Carboxylic acids: carbonyl group + hydroxyl group B. Esters: RCO2R' or RCOOR', where a carbonyl group is boned to an alkoxyl (-OR) group. C. Amides: RCONH2, RCONHR', RCONR'R'' , where the carbonyl group bond to the nitrogen atom baring hydrogen and/ or alkyl group. Nitriles: R—CN. Sp hybridized. Acentronitrile: Butanentrile: Cyclic nitriles are named by adding –carbonitrile to the name often ring system to which the -CN group is attached. Benzenecarbonitrile (benzonitrile, C6H5CN): Cyclohexanecarbonitrile: Lewis Acid/ Bases Acids are electron pair acceptors: Base are electron pair donors: Infrared Spectrum Infrared spectroscopy depends on the interaction of molecules or atoms with electromagnetic radiation. IR causes atoms and groups of atoms of organic compounds to vibrate with increased amplitude about the covalent bonds that connect them. The functional groups of organic molecules include specific arrangements of bonded atoms ,absorption of IR radiation will occur at specific frequencies characteristic of the type of bond and atom presented. Formula: Formula for frequency: Formula for energy of absorption (E): inversely proportional to frequency of radiation (v) Molecules movement: Two atoms joined by a covalent bond can undergo a stretching where atoms move back and forth as if joint by spring. Stretching vibration: Systematic stretching: Asymmetric stretching: Scissoring (in plane): Rocking (in plane): Wagging (out of plane): Twisting (out of plane: Frequency related mass 1. The mass of bonded atoms: light atoms vibrate at higher frequencies than heavier ones 2. The relative stiffness of the bond triple > double > single Nonmenclature Alkanes: methane (CH4), Ethane (CH3CH3), Propane: CH3CH2CH3, Butane: CH3CH2CH2CH3 Pentane: C5 Hexane: C6 Heptane: C7 Octane: C8 Nonane: C9 Decane: C10 Butane: C4H10 Isobutane: C4H10 How
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