Chapter 1 Introduction to Organic Chemistry: 1.1 Organic Compounds 1

Organic Chemistry An organic compound is a compound made from carbon atoms. has one or more C atoms. has many H atoms. may also contain O, S, N, and halogens. 2

Organic Chemistry They are everywhere in our daily life ◦ foods, flavors and fragment ◦ Medicines, toiletries and cosmetics ◦ Plastics, films, fibers and resins ◦ All other living organisms

Organic Compounds Typical organic compounds have covalent bonds. have low melting points. have low boiling points. are flammable. are soluble in nonpolar solvents. are not soluble in water. 4 oil (organic) and water (inorganic)

Organic vs. Inorganic Propane, C 3 H 8, is an organic compound used as a fuel. NaCl, salt, is an inorganic compound composed of Na + and Cl − ions. Why is propane organic, but NaCl is not? 5

Examples Identify each characteristic as most typical of compounds that are 1) inorganic or 2) organic. A. has a high melting point. B. is not soluble in water. C. has a formula CH 3 ─CH 2 ─CH 3. D. has a formula MgCl 2. E. burns easily in air. F. has covalent bonds. 6

1.2 Where do we obtain Organic compounds? Two principal ways: ◦ isolation from nature  is to extract and purify them from biological sources ◦ synthesis in the laboratory

Synthesis in the Laboratory Using different methods to made an organic compound or develop their derivatives

Lewis Structures represents how an atom’s valence electrons are distributed in a molecule Show the bonding involves (the maximum bonds can be made) Try to achieve the noble gas configuration The valence-shell electron-pair repulsion (VSEPR) model tell us the common angles about the carbon atoms

Writing Dot Lewis Structure: Rules for multiple atoms Duet Rule: sharing of 2 electrons ◦ E.g H 2  H : H Octet Rule: sharing of 8 electrons ◦ Carbon, oxygen, nitrogen and fluorine always obey this rule in a stable molecule ◦ E.g F 2, O 2 Bonding pair: two of which are shared with other atoms Lone pair or nonbonding pair: those that are not used for bonding

1.3 How do We Write Structural Formulas of Organic Compounds? A hydrogen molecule is stable with 2 electrons (helium). has a shared pair of electrons.

12 Multiple Bonds In a nitrogen molecule, N 2, each N atom shares 3 electrons. each N attains an octet. the bond is a multiple bond called a triple bond. the name is the same as the element.

13 Carbon Forms 4 Covalent Bonds Carbon normally forms four covalent bonds and has no unshared pairs of electrons E.gIn a CH 4 (methane) molecule, 1 C atom shares electrons with 4 H atoms to attain an octet. each H atom shares 1 electron to become stable, like helium.

Bonding in Methyl Cation, the Methyl Radical, and the Methyl Anion Not all carbon atoms form four bonds

General rules for Writing Dot Lewis structure involving N, O, H and Halogens Nitrogen normally forms three covalent bonds and has one unshared pair of electrons Oxygen normally forms two covalent bonds and has two unshared pairs of electrons A halogen (fluorine, chlorine, bromine, and iodine) normally forms one covalent bond and has three unshared pairs of electrons

16 Some Electronegativity Values for Group A Elements Low values High values ` Electronegativity increases ` Electronegativity decreases Copyright © 2009 by Pearson Education, Inc.

Polar Covalent Bonds: Electronegativity NaCl HCl Cl 2

Writing Dot Lewis Structure with multiple center atoms Carbons will also be the center atom in the organic molecule ◦ -C-C-C- chains Hydrogen is connected to carbon unless it’s an oxyacids (HClO, etc..) or Carbon has no more valence electrons to share Order of increasing EN ◦ (least) C  N  O  F (most)

Examples Write a Dot Lewis structure for the following atoms, molecules and ions ON H 2 SCN- CO 3 2- C 2 H 2 N 2 H 4 CH 2 Cl 2

Write a Dot Lewis structure for CH3COOH

Example Write a Dot Lewis Structure for CH 3 NH 2

VSEPR Theory VSEPR theory proposes that the geometric arrangement of terminal atoms, or groups of atoms about a central atom in a covalent compound, or charged ion, is determined solely by the repulsions between electron pairs present in the valence shell of the central atom Common shape and angles ◦ Linear (180 o ) ◦ Tetrahedral (109.5 o ) ◦ Trigonal planar (120 o ) See table 1.2 page 5

Examples Complete the following Dot Lewis structure by adding the missing lone-pair then predict the bond angles a. b. c.

25 Elements in Organic Compounds In organic molecules, carbon atoms bond with four bonds. mostly with H and other C atoms. sometimes to O, N, S. sometimes to halogens F, Cl, and Br. Table 1.3 page 7

26 Functional groups are a characteristic feature of organic molecules that behave in a predictable way. composed of an atom or group of atoms. groups that replace a hydrogen atom in the corresponding alkane. a way to classify families of organic compounds. Functional Groups

Alcohol An alcohol contains the hydroxyl (-OH) functional group. R-OH

Writing structural formulas of Alcohol CH 4 O Molecular formula CH 3 OH Condensed formula

Writing structural Formulas of Alcohols Draw Lewis structure and condensed structural formulas for the four alcohol with molecular formula C 4 H 10 O. Classify each alcohol as primary, secondary or tertiary. ◦ Hints: Consider the connectivity of the four carbon atoms; they can be bonded either four in a chain or three in a chain with the fourth carbon as a branch on the middle carbon. Then consider which carbon should connect to OH with having the same molecule

Amines In amines, the functional group is a nitrogen atom. RNH 2, R 2 NH or R 3 N

Examples Draw structural formulas of the three secondary amines with the molecular formula C 4 H 11 N

Ketone and Aldehyde Aldehyde contains a carbonyl group bonded to a hydrogen Ketone contains a carbonyl group bonded to two carbon atoms

Carboxylic Acids Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group. –COOH O ║ — C—OH

Examples Draw condensed structural formulas for the two carboxylic acids with molecular formula C 4 H 8 O 2

Carboxylic esters An ester contains the carboxyl group between carbon atoms. –COOR or –CO 2 R

Examples Draw structural formulas for the four esters with the molecular formula C 4 H 8 O 2

37 Learning Check Classify each of the following as: alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, or amide. 1)CH 3 ─CH 2 ─CH 2 ─OH 2) CH 3 ─O─CH 2 ─CH 3 3) CH 3 ─CH 2 ─NH 2 O O ║ ║ 4) CH 3 ─C─OH 5) CH 3 ─C─O─CH 3

Examples Consider the formula C 4 H 8 O 2. Write the structural formula for this molecular formula with ◦ A carboxyl group ◦ Ketone group and a 2 o alcohol group ◦ An aldehyde and a 3 o alcohol group ◦ A carbon-carbon double bond and a 1 o alcohol