Organic & Biological Chemistry Chemistry of Life Alkanes (Saturated HCs) Hydrocarbons Alcohols Ethers Functional Groups Biochemistry CarbohydratesProteinsNucleic Acids Chirality Alkenes (Unsaturated HCs) 2/17/2016 The Structures of Organic Molecules Organic molecules exhibit three different types of hybridization at the carbon center: sp 3 hybridized carbons for tetrahedral geometries; sp 2 hybridized carbons for trigonal planar geometries; and sp hybridized carbons for linear geometries. Some General Characteristics of Organic Molecules Drawing Lewis Structures Follow Step by Step Method (See Ng Web-site)See Ng Web-site 1.Total all valence electrons. [Consider Charge] 2.Write symbols for the atoms and guess skeleton structure [ define a central atom ]. 3.Place a pair of electrons in each bond. 4.Complete octets of surrounding atoms. [ H = 2 only ] 5.Place leftover electrons in pairs on the central atom. 6.If there are not enough electrons to give the central atom an octet, look for multiple bonds by transferring electrons until each atom has eight electrons around it. HyperChem CyberChem video Figure 9.3 HyperChem Summary of VSEPR Molecular Shapes e-pairsNotation Name of VSEPR shape Examples 2AX 2 LinearHgCl 2, ZnI 2, CS 2, CO 2 3AX 3 Trigonal planarBF 3, GaI 3 AX 2 ENon-linear (Bent)SO 2, SnCl 2 4AX 4 TetrahedralCCl 4, CH 4, BF 4 - AX 3 E(Trigonal) PyramidalNH 3, OH 3 - AX 2 E 2 Non-Linear (Bent)H 2 O, SeCl 2 5AX 5 Trigonal bipyramidalPCl 5, PF 5 AX 4 EDistorted tetrahedral (see-sawed) TeCl 4, SF 4 AX 3 E 2 T-ShapedClF 3, BrF 3 AX 2 E 3 LinearI 3 -, ICl 2 - 6AX 6 OctahedralSF 6, PF 6 - AX 5 ESquare PyramidalIF 5, BrF 5 AX 4 E 2 Square PlanarICl 4 -, BrF 4 - See Ng Web-site HyperChemCyberChem video Methane Ethene Ethyne Figure 9.14: Covalent Bonding and Orbital Overlap Some General Characteristics of Organic Molecules sp 3 Hybridzation in Carbon Bonding Hydrocarbons are compounds with only C and H. Four classes: alkanes (all bonds and no bonds); alkenes (a mixture of and bonds, but no triple bonds); alkynes (must contain triple bonds); and aromatics (have planar, ring structures with alternating single and double bonds). Saturated compounds have only bonds. Unsaturated compounds have both and bonds. Introduction to Hydrocarbons AlkanesAlkanes HyperChem Structural Isomers AlkanesAlkanes Nomenclature AlkanesAlkanes 1.Find longest continuous chain of carbon atoms, and use name of this chain (see Table 25.1) as the base name of the compound. 2.Number the carbon atoms in the longest chain, beginning with end of chain that is nearest to a substituent. 3.Name and give the location of each substituent group. 4.When two or more substituents are present, list them in alphabetical order. PrefixBaseSuffix What SubstituentHow many carbonsWhat Family Cycloalkanes AlkanesAlkanes Reactions of Alkanes The C-C and C-H bonds are very strong. Therefore, alkanes are very unreactive. At room temperature alkanes do not react with acids, bases, or strong oxidizing agents. Alkanes do combust in air (making them good fuels): 2C 2 H 6 (g) + 7O 2 (g) 4CO 2 (g) + 6H 2 O(l) H = kJ AlkanesAlkanes Alkenes Geometrical isomers are possible since there is no rotation about a C=C bond. Note the overlap between orbitals is above and below the plane of the bonds. As the C-C bond begins to rotate (moving from cis to trans) the overlap decreases. Unsaturated Hydrocarbons Alkenes At 90 the bond breaks completely. Therefore, there is no rotation about a bond. Therefore, cis and trans isomers do not readily interconvert. Unsaturated Hydrocarbons Alkynes Alkynes are hydrocarbons with one or more C C bond. Therefore, alkynes have one and two bonds between two C atoms. Ethyne (acetylene) is a reactive alkyne: HC CH. When acetylene is burned in the presence of oxygen (oxyacetylene torch) the temperature is about 3200 K. Alkynes are named in the same way as alkenes with the suffix -yne replacing the -ene for alkenes. Unsaturated Hydrocarbons Addition Reactions of Alkenes and Alkynes The most dominant reaction for alkenes and alkynes involves the addition of something to the two atoms which form the double bond: Note that the C-C bond has been replaced by two C-Br bonds. Unsaturated Hydrocarbons Aromatic Hydrocarbons Aromatic structures are formally related to benzene. Benzene is not reactive because of the stability associated with the delocalized electrons. Unsaturated Hydrocarbons Functional Groups: Alcohols and Ethers Carboxylic Acids Compounds with a Carbonyl Group A molecule that exists as a pair of nonsuperimposable mirror images is called chiral. Organic compounds that contain one carbon atom that is attached to four different atoms or groups are chiral. The carbon atom attached to the four different moieties is called a stereogenic carbon. Chirality in Organic Chemistry S-ibuprofen: Chemistry of living organisms is called biochemistry. Biochemical molecules tend to be very large and difficult to synthesize. Living organisms are highly ordered. Therefore, living organisms have very low entropy. Most biologically important molecules are polymers, called biopolymers. Biopolymers fall into three classes: proteins, polysaccharides (carbohydrates), and nucleic acids. Introduction to Biochemistry Amino Acids Proteins are large molecules present in all cells. They are made up of - amino acids. ProteinsProteins Protein Structure Pitch is the distance between coils. The pitch and diameter ensure no bond angles are strained and the N-H and carbonyl functional groups are optimized for H-bonding. Tertiary structure is the three dimensional structure of the protein. Video Summary CarbohydratesCarbohydrates Carbohydrates have empirical formula C x (H 2 O) y. Carbohydrate means hydrate of carbon. Most abundant carbohydrate is glucose, C 6 H 12 O 6. Carbohydrates are polyhydroxy aldehydes and ketones. Glucose is a 6 carbon aldehyde sugar and fructose 6 carbon ketone sugar. The alcohol side of glucose can react with the aldehyde side to form a six-membered ring. Disaccharides Lactose is formed from galactose and -glucose. Sucrose is about six times sweeter than lactose, a little sweeter than glucose and about half as sweet as fructose. Disaccharides can be converted into monosaccharides by treatment with acid in aqueous solution. CarbohydratesCarbohydrates Polysaccharides Bacteria in the stomach of animals contain cellulases, which are enzymes that enable animals to use cellulose for food. CarbohydratesCarbohydrates Nucleic acids carry genetic information. DNA (deoxyribonucleic acids) have molecular weights around 10 6 amu and are found inside the nucleus of the cell. RNA (ribonucleic acids) have molecular weights around 20,000 to 40,000 amu and are found in the cytoplasm outside the nucleus of the cell. Nucleic acids are made up of nucleotides. Nucleic Acids Organic & Biological Chemistry Chemistry of Life Alkanes (Saturated HCs) Hydrocarbons Alcohols Ethers Functional Groups Biochemistry CarbohydratesProteinsNucleic Acids Chirality Alkenes (Unsaturated HCs) Saturated compounds have only bonds. Unsaturated compounds have both and bonds.