Chapter 3: Introduction to Organic Chemistry III PDF

College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ Chapter 3: Introduction to Organic Chemistry III Chemistry Department CHEM 1450 College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ After this lecture, the student will be able to: } Explain the difference between the old and new concept of organic compounds } Explain why organic che...

College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ Chapter 3: Introduction to Organic Chemistry III Chemistry Department CHEM 1450 College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ After this lecture, the student will be able to: } Explain the difference between the old and new concept of organic compounds } Explain why organic chemistry is named as the chemistry of carbon } Explain why a carbon atom forms four covalent bonds. } Illustrate the different forms of hydrocarbons and the saturation state of bonds } Identify two possible arrangements of carbon atoms in an alkane } Identify the IUPAK system in naming organic compounds } Explain the IUPAK rules in naming hydrocarbons College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ } } } } In the early days of chemistry, scientists classified chemical substances into 2 groups: Inorganic: those that were composed of minerals, such as rocks and nonliving matter Organic: those that were produced by living organisms, hence the name “organic” At the time, scientists believed that a “vital force”, only present in living organisms, was necessary to produce organic compounds. College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ } In 1828, German chemist Friedrick Wöhler disproved this theory by producing urea, an organic compound found in urine, from inorganic compounds NH4NCO → H2N-CO-NH2 (INORGANIC) (ORGANIC) } } Now organic chemistry is defined as the study of compounds containing carbon atom There are currently about 10 million organic compounds known to man College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ } } The simplest organic compounds are called hydrocarbons A hydrocarbon is an organic compound that contains only carbon and hydrogen College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ ◦ Recall that a carbon atom has four valence electrons and a hydrogen atom has one valence electron. So, one carbon atom can form a single covalent bond with four hydrogen atoms as shown: College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ Because carbon has four valence electrons, a carbon atom always forms four covalent bonds. There is a carbon-carbon bond in ethane The ability of carbon to form stable carbon-carbon bonds is one reason that carbon can form so many different compounds College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ ◦ The electron pair in a carbon-hydrogen or a carboncarbon bond is shared almost equally by the nuclei of the atoms forming the bond. ◦ Thus, hydrocarbons are nonpolar molecules. ‘ The attractions between nonpolar molecules are weak van der Waals forces. ‘ So, hydrocarbons with low molar masses tend to be gases or liquids that boil at a low temperature. College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ Recall the general rule “like dissolves like.” ◦ A nonpolar compound and a polar compound will not form a solution. ◦ For example, because oil is a mixture of hydrocarbons, oil and water do not mix. College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ ◦ Because a carbon atom forms four covalent bonds, it can bond not only to one or two other carbon atoms, but also to three or even four other carbons, resulting in branched chains. ◦ In organic chemistry, branches on a hydrocarbon chain are discussed as if they were substituted for a hydrogen atom on the chain. ‘ An atom or group of atoms that can take the place of a hydrogen atom on a parent hydrocarbon molecule is called a substituent. ‘ So, carbon atoms in a hydrocarbon can be arranged in a straight chain or in a chain that has branches College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ } } } } } } } } } } Methane,CH4 Ethane, CH3CH3 Propane, CH3CH2CH3 Butane, CH3CH2CH2CH3 Pentane, CH3CH2CH2CH2CH3 Hexane, CH3CH2CH2CH2CH2CH3 Heptane, CH3CH2CH2CH2CH2CH2CH3 Octane, CH3CH2CH2CH2CH2CH2CH2CH3 Nonane, CH3CH2CH2CH2CH2CH2CH2CH2CH3 Decane, CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ Alkyl groups are named by removing the -ane ending from the parent hydrocarbon name and adding –yl Alkane – H = Alkyle gp College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ Each carbon in an organic molecule can be categorized as a primary, secondary, tertiary, or quaternary carbon.  If the carbon atom has only one carbon attached to it, then the carbon is a primary carbon.  If two carbons are attached to the carbon atom, the carbon is a secondary carbon; if three carbons, a tertiary carbon; and if four carbons, a quaternary carbon. College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ } Select the longest continuous chain of carbon atoms as the parent compound. } Number the carbon atoms in the parent carbon chain starting from the end closest to the first carbon atom that has an alkyl or other group. } Name the alkyl group and designate the position on the parent carbon chain by a number. } When the same alkyl group branch chain occurs more than once, indicate this repetition by a prefix (di-, tri-, tetra-, and so forth). } When several different alkyl groups are attached to the parent compound, list them in alphabetical order. College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ 5 CH 3 4 CH 2 3 CH 2 2 CH CH3 pentane 1 CH 3 parent alkane College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ 5 CH3 4 CH2 3 CH2 2 CH CH3 1 C H3 alkyl group methylpentane College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ 55 CH3 44 CH2 33 CH2 22 CH 11 C H3 CH3 2-methylpentane College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ College of Medicine – ‫ﻛﻠﯾﺔ اﻟطب‬ 5. Draw the structural formula for 2,2,4-trimethylpentane, or isooctane?