Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior...

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Ms. Kiely IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry

Transcript of Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior...

Page 1: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

Ms. KielyIB Chemistry (SL)Coral Gables Senior High School

Topic 10Organic Chemistry

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Organic ChemistryOrganic chemistry: focuses on molecular compounds that contain carbon in them; most specifically those that exist or pertain to* living systems, are a product of something once living.

-an organic compound ALWAYS contains carbon, and almost always also includes hydrogen.

-all organic compounds are covalently bonded.

-Other elements, such as oxygen, nitrogen, chlorine, and sulfur are often also present, but it is carbon that is the key.

*many organic molecules can be synthesized, making them technically not “organic”

Page 3: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses
Page 4: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

Organic ChemistryCarbon is able to form a larger number of compounds than all the other elements put together! This is because of carbon’s four valence electrons, allowing it to make four strong covalent bonds.

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Alkanes, Alkenes, AlkynesOrganic compounds can be classified into different categories or “families”. For example, we can classify each of the following groups as aHomologous series: a group of compounds that share common features

● Alkanes: a hydrocarbon compound in which only single covalent bonds exist; the carbon-carbon bonds are single, and so are the carbon-hydrogen bonds of course. (Hydrogen can only make a single covalent bond.)

● Alkenes: a hydrocarbon compound that contains one or more carbon-carbon double covalent bond.

● Alkynes: a hydrocarbon compound that contains one or more carbon-carbon triple covalent bond.

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1. A constant increment of change in molecular structure for the successive molecules in a series. For example, successive members of a homologous series differ by a CH₂ group

2. Members of a homologous series can be represented by the same general formula.

3. Members of a homologous series show a gradation in physical properties.

4. Members of a homologous series show similar chemical properties.

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A homologous series is a group of organic compounds that are put into a “family” or “series” based on common features the compounds in that series share. The first common feature is:

1. Successive members of a homologous series differ by a CH₂ group.

Neighboring members of the alkanes, for example, indeed differ from each other by a CH₂ group.

CH₄ + CH₂ = C₂H₆ Methane + CH₂ = Ethane

C₂H₆ + CH₂ = C₃H₈ Ethane + CH₂ = Propane

C₃H₈ + CH₂ = C₄H₁₀

Propane + CH₂ = Butane etc.

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2. Members of a homologous series can be represented by the same general formula:

In the case of the alkanes, for example, the general formula would be CnH2n+2

If n=1, then CnH2n+2 = CH4, methane

If n=2, then CnH2n+2 = C2H6, ethane

If n=3, then CnH2n+2 = C3H8, propane

If n=4, then CnH2n+2 = C4H10, butane

etc.

Page 9: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

3. Members of a homologous series show a gradation in physical properties:In the case of the alkanes, for example, the boiling points increase with increasing

carbon number. This increasing pattern of boiling point with increasing carbon number is due to fact that alkanes, (just like alkenes and alkynes), are indeed covalently bonded together, but are attracted to each other via London (dispersion) forces.

The larger an alkane is, the more availability it has to cause dipole induced attractions to other alkanes; meaning, the bonds are “stronger” and thus more difficult to “boil apart”.

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4. Members of a homologous series show similar chemical properties.

Since the members of a homologous series share similar physical properties, they also share similar chemical properties, such as similar chemical reactivity when reacting with other substances.

Identifying a homologous series’ functional group, for example, is a great way to determine what that groups’ specific chemical properties are.

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Functional GroupsA functional group is a small specific group of atoms that are attached to a carbon atom in an organic molecule, or a type of bond in a compound.

Functional groups give molecules their characteristic properties. The functional group is the reason that a homologous series behaves the way it does. All molecules that have the same functional group will belong to the same homologous series.

Notice that the following compounds, which all belong to the homologous series known as the alcohols: 1) each possess the functional group -OH, and 2) differ successively by a CH₂ group.

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Functional GroupsRemember that members of a homologous series can be represented by the same general formula:

In the case of the alcohols, which all have the same functional group, -OH, the general formula would be CnH2n+1OH

If n=1, then CnH2n+1OH = CH3OH, methanol

If n=2, then CnH2n+1OH = C2H5OH, ethanol

If n=3, then CnH2n+1OH = C3H7OH, propanol

If n=4, then CnH2n+1OH = C4H9OH, butanol

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Fig: examples of some functional groups.

*Alkanes do not have a functional group. You can consider them the basic building blocks of all organic molecules.

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Practice

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ANSWER

Is the only option where each molecule

successively differs by a CH2 group.

Page 16: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

The study of organic chemistry in some ways is like studying a language.

The IUPAC, International Union of Pure and Applied Chemistry, has made very specific rules for naming substances, which have enabled international communication on such substances to be clear and consistent.

Basically, these rules seem annoying and unnecessary, but are actually essential and extremely helpful in identifying EXACTLY what a scientist is working with, how it looks, how it will react, etc.

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In order to describe molecules in these such ways that have been determined by the IUPAC, we must take into consideration the following:

-the formula used to represent a molecule

-the specific name given to the molecule, known as its nomenclature

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As stated before, alkanes, alkenes, and alkynes are three different homologous series of aliphatic hydrocarbons.

● Alkanes: hydrocarbon with only single carbon-carbon covalent bonds.● Alkenes: hydrocarbon that contains at least one or more carbon-carbon double

covalent bond. Other bonds may be single carbon-carbon bonds and carbon-hydrogen bonds.

● Alkynes: hydrocarbon compound that contains at least one or more carbon-carbon triple covalent bond. Other bonds may be single or double carbon-carbon bonds and carbon-hydrogen bonds.

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Nomenclature in general1. Identify the longest chain of carbon atoms, because this chain gives the stem of the name. For instance, with alkanes we can refer to the image here:

2. Identify the functional group (pg. 314), as the functionalgroup is what supplies the suffix of the name. For the alkanes, that functional group gives the -ane suffix.

3. Identify side chains or substituent groups. These are groups of atoms that branch off of a carbon in the compound.We will discuss them in slides to come.

Let’s first practice all these naming rules using the Alkanes.

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Nomenclature of AlkanesLet’s learn to name alkanes first in order to better understand the rules of nomenclature for all organic compounds. There are I) straight-chain alkanes, and II) branched-chain alkanes.

I. Straight-chain alkanes are alkanes, (hydrocarbons composed only of single covalent bonds), that contain any number of carbon atoms one after the other in a chain.

Ethane, C2H6 Propane, C3H8

Butane, C4H10

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Nomenclature of Straight-Chain Alkanes1. For the straight-chain alkanes with 1 - 4 carbon atoms, the stems are: meth-, eth-, prop-, but- (Me et Pro bu).

The straight-chain alkanes with 5 or more carbons, their stems are quite easy since they are based on commonly used Latin or Greek numerical prefixes: pent- for 5, hex- for 6, hept- for 7, and so on.

2. The functional group is the alkane itself, which, according to pg. 314, means that the names contain an -ane suffix.

3. We won’t add substituents just yet for straight-chained alkanes- so we will revisit this step later when we get to branched-chained alkanes.

Page 22: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

PRACTICE

Name the following molecules:

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Drawing Structural Formulas for Straight-Chain Alkanes 1. Look at the prefix of the name in order to determine how many carbon atoms are linked together in a straight chain made up of single covalent bonds (represented by single lines).

2. Using single covalent bonds, place hydrogen atoms around the carbon atoms, so that each carbon atom and each hydrogen reaches its version of the octet rule. Remember, hydrogen only needs to have 2 valence electrons to feel “stable”.

3. Double check that you have only drawn the type and respective amounts of atoms that the formula calls for.

Page 24: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

PracticeDraw the following:

1) Octane2) Propane

Page 25: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

Nomenclature of Branched-Chain AlkanesII) Branched-chain alkanesBecause a carbon atom forms four covalent bonds, it can bond not only to one or two other carbon atoms, but also to three or four other carbons, meaning it can also attach to a carbon that is attached to other atoms! This results in what we call branched chains.

In organic chemistry, we refer to branches on a hydrocarbon chain as if they were “substitutes” for a hydrogen that would originally go there. Therefore, an atom or group of atoms that can take the place of a hydrogen atom on a parent hydrocarbon molecule is called a substituent.

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You can think of an alkyl group as just an alkane with one of the hydrogens removed. This

alkane here has three substituents attached to it: three alkyl groups that are

referred to as methyl.

These alkyl groups are referred to as methyl since they are methane’s that have one

hydrogen removed.

Nomenclature of Branched-Chain AlkanesII) Branched-chain alkanesA substituent that is derived from an alkane is called an alkyl group. There are many different types of alkyl groups.

*In this case three methyl groups are attached as substituents. Other substances can also attached themselves as substituents to organic molecules: nitrogen, oxygen, chlorine, and sulfur.

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Other common alkyl groups are ethyl, CH2CH3, and propyl, CH2CH2CH3

Branched-chain alkanes are, therefore, straight-chain alkanes that have substituent alkyl groups attached to them, like branches.

Page 28: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

So let’s learn how to name branched-chain alkanes:1. Find the longest continuous chain of carbons in the molecule. This chain is considered the parent hydrocarbon.

2. 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.

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3. 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.

4. Use prefixes to indicate the appearance of the same group more than once in the structural formula. Common prefixes are di-, tri-, and tetra-.

5. List the names of alkyl substituents in alphabetical order. For purposes of alphabetizing, ignore the prefixes di-, tri-, etc.

6. 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.

Page 30: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

Nomenclature of Branched-Chain AlkanesName the following organic molecules:

1.

2.

3.

Page 31: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

Nomenclature of Branched-Chain AlkanesName the following organic molecules:

1.

2.

3.

Page 32: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

Functional groups:A functional group is a small group of atoms that are attached to a carbon atom in a molecule. They are the reactive part of the molecule: this means that the functional group determines how a molecule behaves in a chemical reaction. Pg. 314, Table

Functional groups need to be known since they are integral to naming a compound. When you recognize the functional group in a compound, you are able to determine what the suffix of its name will be.

Additionally, the class names should be known.

The class of a compound refers to the type of compound. The functional group refers to the site of reactivity in the molecule.

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You are expected to be familiar with the nitrogen-

containing functional groups (amine, amide, and nitrile), but nomenclature of these classes of compounds will

not be assessed.

You should know try to be familiar with how to name compounds with the following functional

groups.

Page 34: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

Tips for remembering classes and their functional groups:

-You are expected by IB to be familiar with the amide, amine, and nitrile class (the nitrogen-containing functional groups), BUT the nomenclature of these classes of compounds will not be assessed!

-Make sure not to confuse ethers and esters. Ethers are derived by replacing the H of an alcohol by an alkyl group, while esters are derived by replacing the H of an acid by an alkyl group.

-Aldehyde and ketone have similar functional groups- a good way to remember how they differ is to notice that there is an H in aldeHyde, but not in ketone.

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For Example:

Since it is part of the alkenyl functional group and the Alkene class, we know that the name of this compound will have the suffix -ene.

All we have to do now it count the amount of carbons in the longest chain, number the position of the double bond so that it has the lowest number, and additionally number the position of and name any substituents that might exist on the compound.

This compound has no substituents, is an alkene, and has 3 carbons: Pro-1-pene

This double carbon bond is the functional group of this compound, this is its active site, indicating that it is part of

the Alkene class.

The name of the functional group is the Alkenyl functional group.

Page 36: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

Rules for naming an alkene:Remember that for a compound to be part of the alkene family means that the compound has at least one double bond between carbon atoms.

1. Find the longest carbon chain the molecule that contains the double bond. This chain will have the same prefix as an alkane that has the same number of carbons; however, it will end in -ene instead of -ane.

2. Number the chain so that that carbon atoms of the double bond have the lowest possible numbers.

3. Substituents on the chain are named and numbered in the same way they are for alkanes. However, for alkenes, you additionally include the number that indicates where the double bond is located.

*These rules are the same for alkynes, except for triple bonds instead of double.

Page 37: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

Examples:What are the names of the following compounds?1. 3.

2.

Page 38: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

Examples:What are the names of the following compounds?1. 3.

but-1-ene, a.k.a butene-1 but-2-ene, a.k.a butene-2

2.

pent-2-ene, a.k.a pentene-2

Page 39: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses
Page 40: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

23) A24) B

Page 41: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

Saturated & Unsaturated compoundsA saturated compound is one that only contains single bonds, and therefore contains the maximum number of hydrogen atoms per carbon atom in its structure; for example, the alkanes.

An unsaturated compound contains double or triple bonds, therefore, the ratio of hydrogen to carbon atoms is lower than in a saturated compound; for example, the alkenes and alkynes.

Unsaturated compounds are more reactive (less stable)

than saturated compounds.

Page 42: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

You can therefore figure that the way an organic molecule will react in a chemical reaction is dependent on whether the molecule is saturated or unsaturated. For instance, hydrocarbons, such as the alkanes, which are only made up of single bonds and therefore are saturated, are very strong! It is difficult to break their single bonds when compared to the double and triple bonds found in unsaturated compounds. Due to this, saturated compounds are quite unreactive.

This might seem strange at first, but consider that the double or triple bonds in alkenes and alkynes are the sites of reactivity on those respective types of organic compounds. One of the bonds within a double and triple bond is relatively easily broken since double and triple bonds consist of electrons in close proximity- the electrons already want to push away from each other anyway! The breaking of one bond within a double bond or triple bond creates two new bonding positions for a carbon atom- therefore making unsaturated compounds much more reactive!

Page 43: Topic 10 Organic Chemistry - Coral Gables Senior High€¦ · IB Chemistry (SL) Coral Gables Senior High School Topic 10 Organic Chemistry. Organic Chemistry Organic chemistry: focuses

Reference pagesPgs. 306-307

As you study, you will want to refer to these pages. They contain the terms and conventions that are commonly used in organic chemistry, aiding your understanding of the content.