Simple Organic Chemistry

Simple Organic Chemistry
Basic Structure and Nomenclature Graphic:

OBJECTIVES: Describe the relationship between number of valence electrons and bonding in carbon. Define and describe alkanes. Relate the polarity of hydrocarbons to their solubility.

Organic Chemistry and Hydrocarbons
“Organic” originally referred to any chemicals that came from organisms German chemist Friedrich Wohler synthesized urea in a lab from inorganic substances. 1800 – 1882

Organic Chemistry and Hydrocarbons
Over a million organic compounds, with a dazzling array of properties Why so many? Carbon’s unique bonding ability! Let’s start with the simplest of the organic compounds. These are the Hydrocarbons

Hydrocarbons contain only two elements: 1) hydrogen, and 2) carbon
simplest hydrocarbons called “alkanes”, which contain only carbon to carbon single covalent bonds

Carbon has 4 valence electrons, thus forms 4 covalent bonds
methane (CH4) with one carbon is the simplest alkane. It is the major component of natural gas Carbon has 4 valence electrons, thus forms 4 covalent bonds not only with other elements, but also forms bonds WITH ITSELF (nonpolar)

Different Ways of Representing Hydrocarbons
The table below shows the structural formulas, ball-and-stick models, and space-filling models for methane and ethane. Different Ways of Representing Hydrocarbons Name Structural formula Ball-and-stick model Space-filling model Methane Ethane

Properties of Hydrocarbons
The electron pair in a carbon-hydrogen or a carbon-carbon 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.

Recall the general rule “like dissolves like.”
Properties of Hydrocarbons 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.

Alkanes Methane and ethane are examples of alkanes.
An alkane is a hydrocarbon in which there are only single covalent bonds. The carbon atoms in an alkane can be arranged in a straight chain or in a chain that has branches.

Straight-Chain Alkanes
Ethane is the simplest straight-chain alkane, which is an alkane that contains any number of carbon atoms, one after the other, in a chain. Propane (C3H8) has three carbon atoms. Butane (C4H10) has a chain of four carbons. Propane Butane

Melting and Boiling Points Of Straight-Chain Alkanes
Temperature (C) 200 100 –100 –200 Number of carbons 2 4 6 8 10 Melting and Boiling Points Of Straight-Chain Alkanes Melting and boiling points vary with the number of carbons in straight-chain alkanes.

The constant increment of change
Straight-Chain Alkanes Homologous series: The constant increment of change Propane (C3H8) Ethane (C2H6) Butane (C4H10) Increment of change

First Ten Alkanes Formula Name CH4 Methane C6H14 Hexane C2H6 Ethane
Heptane C3H8 Propane C8H18 Octane C4H10 Butane C9H20 Nonane C5H12 Pentane C10H22 Decane Alkane = CnH2n+2 International Union of Pure and Applied Chemistry (IUPAC).

Straight Chain Alkanes aren’t “Straight”
C – C bonds are sp3 hybridized Butane, C4H10

Alkanes Formulas for Butane Formula Description C4H10
Molecular formula Complete structural formula CH3–CH2–CH2–CH3 Condensed structural formula (C–H bonds understood) CH3CH2CH2CH3 (C–H and C–C bonds understood) CH3(CH2)2CH3 (all bonds understood) C–C–C–C Carbon skeleton (hydrogens and C–H bonds understood) Line-angle formula (carbons and hydrogens understood)

Condensed Structural Formula
Explicit hydrogens (those required to complete carbon’s valence) are usually left off of drawings of hydrocarbons C1 C2 C3 C4 C1 C2 C3 C4 Line intersections represent carbon atoms

A condensed structural formula in the form of CH3(CH2)nCH3 uses a different kind of shorthand. The CH2 unit in parentheses is called a methylene group. The subscript n to the right of the parentheses indicates the number of methylene groups that are linked together.

This shorthand method applies to butane as follows: The subscript after the parentheses in the condensed structural formula for butane is 2. This means two methylene groups are linked together in the structure.

Drawing Structural Formulas for Alkanes
Draw complete structural formulas for the straight-chain alkanes that have a. three carbon atoms. b. four carbon atoms.

1 Solve Apply the concepts to this problem. Start with the number of carbons. a. b.

Solve Apply the concepts to this problem.
Each center carbon bonds to two hydrogens. Each end carbon bonds to three hydrogens. a. b. 2 Make sure each carbon has 4 bonds.

Alkanes Branched-Chain Alkanes
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.

Branched-Chain Alkanes
The longest continuous carbon chain of a branched-chain hydrocarbon is called the parent alkane. All other carbon atoms or groups of carbon atoms are regarded as substituents.

A hydrocarbon substituent that is derived from an alkane is called an alkyl group. You can think of any alkyl group as just an alkane with one of the hydrogens removed. Alkyl groups are named by removing the -ane ending from the parent hydrocarbon name and adding -yl.

The three smallest alkyl groups are
Branched-Chain Alkanes The three smallest alkyl groups are the methyl group (–CH3) the ethyl group (–CH2CH3) the propyl group (–CH2CH2CH3) An alkane with one or more alkyl groups is called a branched-chain alkane.

Each carbon in an organic molecule can be categorized as a primary, secondary, tertiary, or quaternary carbon. If the carbon in question has only one carbon attached to it, then the carbon is a primary carbon. If two carbons are attached to the carbon in question, the carbon is a secondary carbon; if three carbons, a tertiary carbon; and if four carbons, a quaternary carbon.

Examples of primary, secondary, tertiary, and quaternary carbons are labeled in the structural formulas below.

Isooctane is a hydrocarbon that contains each of these types of carbons. Isooctane is the standard for determining octane ratings of the mixtures of hydrocarbons that make up gasoline.

The IUPAC rules for naming branched-chain alkanes are quite straightforward. The name of the branched-chain alkane is based on the name of the longest continuous carbon chain. Each substituent is named according to the length of its chain and numbered according to its position on the main chain.

The compound with the following structural formula can be used as an example.

Find the longest continuous chain of carbons in the molecule. This chain is considered the parent hydrocarbon. The longest chain is highlighted in the example. It contains seven carbon atoms. So, the parent hydrocarbon is heptane.

Number the carbons in the main chain in sequence. To do this, start at the end that will give the substituent groups attached to the chain the smallest numbers. Numbering the chain from right to left gives the substituents the lowest numbers (2, 3, and 4).

Add numbers to the names of the substituent groups to identify their positions on the chain. These numbers become prefixes to the name of the substituent group. The substituents and positions are 2-methyl, 3-methyl, and 4-ethyl.

Use prefixes to indicate the appearance of the same group more than once in the structural formula. Common prefixes are di- (twice), tri- (three times), and tetra- (four times). The two methyl groups are combined as 2,3-dimethyl in the name.

List the names of alkyl substituents in alphabetical order. For purposes of alphabetizing, ignore the prefixes di-, tri-, and so on. The 4-ethyl group is listed first, followed by the 2,3-dimethyl.

Combine all the parts and use proper punctuation. Write the entire name without any spaces. Use commas to separate numbers, and use hyphens to separate numbers and words. The correct name of the compound is 4-ethyl-2,3-dimethylheptane.

Naming Branched-Chain Alkanes
Name this compound using the IUPAC system. Notice that the longest chain is not written in a straight line.

1 Identify the longest carbon chain in the molecule. The longest chain has six carbons, so the name ends with hexane.

2 Identify the substituents and their positions on the parent hydrocarbon. There are two methyl substituents on carbon 3, so the prefix is 3,3-dimethyl. Remember to start numbering at the end that gives the substituents the smallest numbers!

2 Put everything together. You can skip the alphabetizing step because there is only one type of substituent. The correct IUPAC name is 3,3-dimethylhexane.

Alkanes With the name of a branched-chain alkane and knowledge of IUPAC rules, it is easy to reconstruct the structural formula. Find the root word (ending in -ane) in the hydrocarbon name. Then, draw the longest carbon chain to create the parent hydrocarbon, and number the carbons in the chain. Identify the substituent groups in the hydrocarbon name. Attach the substituents to the numbered parent chain at the proper positions. Complete the structural formula by adding hydrogens as needed.

Drawing Structural Formulas for Branched-Chain Alkanes
Draw the structural formula for 2,2,4-trimethylpentane, or isooctane.

Draw the structural formula for 2,2,4-trimethylpentane.
Solve Apply the concepts to this problem. Draw the structural formula for 2,2,4-trimethylpentane. Draw the number of carbons needed to represent the parent structure indicated in the name, and number the carbons on the chain. The parent structure is pentane, which has five carbon atoms.

Solve Apply the concepts to this problem. Draw the structural formula for 2,2,4-trimethylpentane. Attach each substituent as indicated in the prefix. There are two methyl groups on carbon 2 and one on carbon 4. 2

Solve Apply the concepts to this problem. Draw the structural formula for 2,2,4-trimethylpentane. Finish by adding hydrogens where needed in the formula. A total of nine hydrogens need to be added to complete the structure. 2 Be careful: Each carbon has four, and only four, bonds.

Nomenclature Practice
Name this compound 1 9 carbons = nonane 2 4 3 5 6 7 8 9 Step #1: For a branched hydrocarbon, the longest continuous chain of carbon atoms gives the root name for the hydrocarbon

Name this compound 9 carbons = nonane 1 2 4 3 5 6 CH3 = methyl 7 chlorine = chloro 8 9 Step #2: When alkane groups appear as substituents, they are named by dropping the -ane and adding -yl.

Name this compound 9 carbons = nonane 1 2 4 3 5 6 CH3 = methyl 7 chlorine = chloro 8 9 1 9 NOT 9 1 Step #3: The positions of substituent groups are specified by numbering the longest chain of carbon atoms sequentially, starting at the end closest to the branching.

Name this compound 9 carbons = nonane 1 2 4 3 5 6 CH3 = methyl 7 chlorine = chloro 8 9 2-chloro-3,6-dimethylnonane Step #4: The location and name of each substituent are followed by the root alkane name. The substituents are listed in alphabetical order (irrespective of any prefix), and the prefixes di-, tri-, etc. are used to indicate multiple identical substituents.

Organic Homework Go to the hand out section and download the page called Organic Chem Homework. Please the completed work to me by 9:30 pm tonight!!

Take this quiz Quiz on Naming Alkane

Alkenes Contain Carbon-Carbon Double bonds
Ethene 1  bond

Alkynes Contain Carbon-Carbon Triple Bonds
Ethyne 1  bond 1  bond

Structural Isomers Look below at the structures of butane and 2-methylpropane. Butane 2-methylpropane

Structural Isomers Butane 2-methylpropane
Even though both compounds have the formula C4H10, their boiling points and other properties differ. Because their structures are different, they are different substances. Compounds that have the same molecular formula but different molecular structures are called isomers. Butane 2-methylpropane

Structural Isomers Butane and 2-methylpropane represent a category of isomers called constitutional isomers, or structural isomers. Structural isomers are compounds that have the same molecular formula but the atoms are joined together differently.

Structural Isomers Stuructrual isomers differ in physical properties such as boiling point and melting point. They also have different chemical reactivities. In general, the more highly branched the hydrocarbon structure is, the lower the boiling point of the isomer will be compared with less branched isomers.

Which of these molecules will have a lower boiling point and why?
Butane 2-methylpropane

Which of these molecules will have a lower boiling point and why?
2-methylpropane will have a lower boiling point because it has a more highly branched structure. Butane 2-methylpropane

Stereoisomers Because molecules are three-dimensional structures, molecules with the same molecular formula and with atoms joined in exactly the same order may still be isomers. Stereoisomers are molecules in which the atoms are joined in the same order but the positions of the atoms in space are different.

Geometric Isoisomers A double bond between two carbon atoms prevents other atoms in the molecule from rotating, or spinning, with respect to each other. Because of this lack of rotation, groups on either side of the double bond can have different orientations in space.

Geometric Isoisomers Cis-Trans Isomers
also known as geometric isomers, have atoms joined in the same order but the spatial orientation of the groups differs. The most common example of cis-trans isomerism occurs in molecules with double bonds.

Cis-Trans Isomers Two arrangements are possible for the methyl groups and hydrogen atoms with respect to the rigid double bond in 2-butene. Opposite sides Same side Cis configuration Trans configuration

Stereoisomers Cis-Trans Isomers
Cis-trans isomers have different physical and chemical properties. You should be able to identify cis-trans isomers of alkenes when each carbon of the double bond has one substituent and one hydrogen.

Stereoisomers Enantiomers
The second category of stereoisomerism occurs whenever a central atom has four different atoms or groups attached. Most commonly the central atom is carbon.

A carbon with four different atoms or groups attached is an asymmetric carbon. In the compound shown here, H, F, Cl, and Br atoms are attached to a single carbon atom, so the carbon is an asymmetric carbon. CHFClBr

The relationship between the two molecules is similar to the relationship between right and left hands. Sometimes the terms right-handed and left-handed are used to describe compounds with an asymmetric carbon.

To understand the stereoisomerism that involves asymmetric carbons, you need to visualize the relationship between an object and its mirror image. If the object is symmetrical, like a ball, then its mirror image can be superimposed. That is, the appearance of the ball and its reflection are indistinguishable.

By contrast, a pair of hands is distinguishable even though the hands have identical parts. The right hand reflects as a left hand, and the left hand reflects as a right hand. When you try to stack your hands on top of one another, the thumb of one hand lines up with the little finger of the other hand. No matter how you turn your hands, you can’t get them to look exactly alike.

Pairs of molecules that are mirror images and not superimposable are called enantiomers, or optical isomers. These molecules are examples of enantiomers.

Unlike other isomers, enantiomers have identical physical properties such as boiling points and densities. Enantiomers do, however, behave differently when they interact with other molecules that have asymmetric carbons. Many molecules in your body have asymmetric carbons, so each enantiomer can have a different effect on the body.

Does a compound have to be smelly in order to be classified as aromatic?
When you hear the word aromatic, you may think of perfume or flowers.

A compound that contains a hydrocarbon ring is called a cyclic hydrocarbon.
Many molecules found in nature contain cyclic hydrocarbons. Rings with five and six carbons are the most abundant.

Cyclic Alkanes Cyclopropane, C3H6 Cyclobutane, C4H8
Cyclopentane, C5H10 Cyclohexane, C6H12 Cycloheptane, C7H14 Remember, explicit hydrogens are left out

Cyclic Hydrocarbons Just as straight-chain and branched-chain alkanes can be either saturated or unsaturated, so can cyclic hydrocarbons. A cyclic hydrocarbon that contains only single bonds, and is therefore saturated is called a cycloalkane.

Cyclic Hydrocarbons To determine the IUPAC name of a cycloalkane, first count the number of carbons in the ring and assign the corresponding alkane name. Name: propane

Cyclic Hydrocarbons Name: cyclopropane
To determine the IUPAC name of a cycloalkane, first count the number of carbons in the ring and assign the corresponding alkane name. Then simply add the prefix cyclo- to the alkane name. Name: cyclopropane

How many hydrogen atoms will a cycloalkane contain in comparison to a straight chain alkane with the same number of carbons?

How many hydrogen atoms will a cycloalkane contain in comparison to a straight chain alkane with the same number of carbons? A cycloalkane will contain two fewer hydrogen atoms than a straight chain alkane with the same number of carbons because there is one additional carbon-carbon bond in the cycloalkane.

Aromatic Hydrocarbons
There is a class of unsaturated cyclic hydrocarbons that are responsible for the aromas of spices such as vanilla, cinnamon, cloves, and ginger. These compounds were originally called aromatic compounds because they have distinct, pleasant aromas. However not all compounds classified has aromatic have pleasant odors, or any odor at all.

Benzene is the simplest aromatic compound. An aromatic compound, or arene, is now defined as an organic compound that contains a benzene ring or other ring in which the bonding is like that of benzene.

The Structure of Benzene The benzene molecule is a six-membered carbon ring with one hydrogen atom attached to each carbon. This arrangement leaves one electron from each carbon free to participate in a double bond. Two different structures with alternating double bonds can be written for benzene.

The Structure of Benzene Drawing a solid or dashed circle inside a hexagon is a good way to represent benzene in terms of how the electrons are distributed. However, such a drawing does not show the number of electrons involved.

Cyclic unsaturated hydrocarbons with delocalized electrons The simplest aromatic hydrocarbon is benzene (C6H6) OR…

Substituted Aromatic Rings Many dyes used to produce the intense colors of your clothing, such as the blue shown here are substituted aromatic compounds.

Substituted Aromatic Rings Compounds containing substituents attached to a benzene ring are named using benzene as the parent hydrocarbon.

Substituted Aromatic Rings When the benzene ring is a substituent, the C6H5 group is called a phenyl group.

Substituted Aromatic Rings Derivatives of benzene with two substituents are called disubstituted benzenes. Dimethylbenzene, also called xylene, is an example of a disubstituted benzene.

Substituted Aromatic Rings There are three constitutional isomers for dimthylbenzene (C6H4(CH3)2). The boiling points of the three compounds are a reminder that constitutional isomers have different physical properties.

Geometric Isomerism in Aromatics
ortho (o-) = two adjacent substituents o-dichlorobenzene meta (m-) = one carbon between substituents m-dichlorobenzene para (p-) = two carbons between substituents p-dichlorobenzene

Substituted Aromatic Rings In the IUPAC naming system, the possible positions of two substituents in disubstituted benzene are designated as 1,2; 1,3; or 1,4. Common names for disubstituted benzenes use the terms ortho, meta, and para (abbreviated as o, m, and p) in place of numbers.

Reactions of Alkenes and Alkynes
Hydrogenation Propene Propane Halogenation 1-Pentene 1-2-dibromopentene Polymerization Small molecules are joined together to form a large molecule Polyethylene

Hydrocarbon Derivatives
Class Functional Group General Formula Alcohol hydroxyl group O — H R – OH Alkyl halide — X R — X Ether — O — R — O — R’ Aldehyde carbonyl group O || — C — H O R — C — H Ketone — C — R — C — R’ Carboxylic acid carboxyl group O — C — OH Ester — C — O— R — C — O — R’ Amine amine group | —N— R’ R — N — R’’

Simple Organic Chemistry

Similar presentations

Presentation on theme: "Simple Organic Chemistry"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Simple Organic Chemistry

Similar presentations

Presentation on theme: "Simple Organic Chemistry"— Presentation transcript:

Similar presentations

About project

Feedback