Class01 ChemistryG12 Notes and Homework

8/4/2019 Class01 ChemistryG12 Notes and Homework

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GRADE12CHEMISTRY

OLYMPIADSCHOOL

. .

FRIDAY4.456.45


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Classifying

Organic Compounds Organic chemistry is the study of compounds that are

based on CARBON. Natural gas, rubbing alcohol,,rose, are all organic compounds.

,

molecules from the basic families of organic compounds.You will be introduced to the shape, structure, and

properties of different types of organic compounds.


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ere are severa m on organ c compoun s, u on yabout a quarter of a million inorganic compoundscom ounds that are not based on carbon . Wh are

there so many organic compounds? The answer lies inthe bonding properties of carbon.

ar on atoms can orm strong s ng e,double, or triple bonds with other carbon atoms.

- ,shared between two carbon atoms. In a double bond,

two pairs of electrons are shared between two atoms. Ina triple bond, three pairs of electrons are sharedbetween two atoms.


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o ecu es a con a n on y s ng e car on-car on on sare saturated. In other words, all carbon atoms arebonded to the maximum number of other atoms: four. Nomore bonding can occur. Molecules that contain doubleor triple carbon-carbon bonds are unsaturated. The

are bonded to less than four atoms each. There ispotential for more atoms to bond to each of these carbonatoms.

Carbon compounds in which carbon forms only single

carbon forms double or triple bonds.


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-

particularly important when the molecule contains polar

covalent bonds. As you may recall from your previousc em s ry course, a po ar cova en on s a cova enbond between two atoms with differentelectronegativities.

Electronegativity is a measure of how strongly an atomattracts electrons in a chemical bond. The electrons in aolar covalent bond are attracted more stron l to the

atom with the higher electronegativity. This atom has apartial negative charge, while the other atom has a

bond dipole: a partial negative charge and a partialpositive charge, separated by the length of the bond.


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-oxygen bond. Oxygen has a higher electronegativity than

carbon. Therefore, the oxygen atom in a carbon-oxygenon as a par a nega ve c arge, an e car on a om

has a partial positive charge.

t er examp es o po ar cova ent on s nc u e , ,and NH. Carbon and hydrogen attract electrons to

almost the same degree. Therefore, when carbon isbonded to another carbon atom or to a hydrogen atom,the bond is not usually considered to be polar. Forexam le, CC bonds are considered to be non- olar.


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OH >

NH >

H2O>


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mo ecu e s cons ere o e po ar, or o ave a

molecular polarity, when the molecule has an overallimbalance of char e. That is the molecule has a re ionwith a partial positive charge, and a region with a partialnegative charge.

urpr s ng y, not a mo ecu es w t po ar on s are po armolecules. For example, a carbon dioxide molecule hastwo olar CO bonds but it is not a olar molecule. Onthe other hand, a water molecule has two polar OH

bonds, and it isa polar molecule.


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,shape of the molecule and the bond dipoles within the

molecule. If equal bond dipoles act in opposite directions in three-

dimensional space, they counteract each other. A

directions is not polar. For exam le, Carbon dioxide, CO2, has two olar CO

bonds acting in opposite directions, so the molecule isnon-polar. Carbon tetrachloride, CCl4, has four polar CCl

. ,tetrachloride is also non-polar.


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t e on po es n a mo ecu e o not

counteract each other exactly, themolecule is polar. Two examples arewater, H2O, and chloroform, CHCl3.

Although each molecule has polar bonds,the bond di oles do not act in exactlopposite directions. The bond dipoles do

molecules are polar.


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orma ys own

structureof

Chloroform

VS.

Spacefilling

Chloroform

(Noticehowyoucan

getasenseforthe

polarityofthemolecule

butnotinthefirst)


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e s eps e ow summar ze ow o pre c w e er ornot a molecule is polar. The Sample Problem that followsives three exam les.

Note: For the purpose of predicting molecular polarity,you can assume that CH bonds are non-polar. In fact,

t ey ave a very ow po ar ty. Step 1 Does the molecule have polar bonds? If your, . ,

2. If a molecule has no polar bonds, it is non-polar.

Examples: CH3CH2CH3 , CH2CH2


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Step 2 Is there more than one polar bond? If your answer is no,see below. If your answer is yes, go to step 3. If a molecule

contains only one polar bond, it is polar. Examples: CH3Cl,

Step 3 Do the bond dipoles act in opposite directions andcounteract each other? Use your knowledge of three-

dimensional molecular shapes to help you answer thisquestion. If in doubt, use a molecular model to help you.

bond dipoles that do not counteract each other, the molecule is

polar. Examples: H2O, CHCl3. If the molecule contains dipolesa coun erac eac o er , e mo ecu e s non-polar.Examples: CO2, CCl4


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. re c an s e c e ree- mens ona s ape arouneach single-bonded atom.

(b) C in CH4

-

multiple-bonded molecule.(a) HCCH

(b) H2CO

3. Identify any polar bonds that are present in eachmo ecu e n ques ons an .


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4. For each molecule in questions 1 and 2,

redict whether the molecule as a whole ispolar or non-polar.


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In this section, we will review the structure and names of

hydrocarbons. As you may recall from your previous,of organic compound.

hydrogen atoms, and are widely used as fuels. Gasoline,propane, and natural gas are common examples of

hydrocarbons. Because they contain only carbon andhydrogen atoms, hydrocarbons are non-polarcompoun s.


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, , An alkane is a hydrocarbon that has only single bonds.

Alkanes that do not contain rings have the formula.

cycloalkane. Cycloalkanes have the formula CnH2n. Analkene is a com ound that has at least one double bond.

Straight-chain alkenes with one double bond have thesame formula as cycloalkanes, CnH2n.


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=me ane

2C=ethane

=

4C=butane

6C=hexane 8C=octane

= 10C=decane


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A double bond involves two pairs of electrons. In a

double bond, one pair of electrons forms a single bond, .electrons in the additional, weaker bond react faster thanthe electrons in the sin le bond. Thus carbon-carbon

double bonds are more reactive than carbon-carbonsingle bonds. When an alkene reacts, the reactiona most a ways occurs at t e s te o t e ou e on .


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A functional group is a reactive group of bonded atomsthat appears in all the members of a chemical family.

.Thus, functional groups help to determine the physicaland chemical ro erties of com ounds.

For example, the reactive double bond is the functionalgroup for an alkene. In this course, you will encounter

many different functional groups.


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An alkyne is a compound that has at least

one tri le bond. A strai ht chain alk newith one triple bond has the formula

.

reactive than double bonds. The functional


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General Rules for Naming Organic

Compounds e nternat ona n on o ure an

Applied Chemistry (IUPAC) has setstandard rules for naming organiccompounds. The systematic (or IUPAC)

names of alkanes and most other organiccompounds follow the same pattern,shown below.

PREFIX + ROOT + SUFFIX


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The Root: How Long Is the Main

Chain? The root of a compounds name indicates

the number of carbon atoms in the main(parent) chain or ring. To determine which

,

chain, or main ring, of the compound. If,

main chain or ring must include themultiple bond.


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The Suffix: What Family Does the

Compound Belong To? The suffix indicates the type of compound, according to

the functional groups present. As you progress through,

chemical families.

,

suffixes -anefor alkanes, -enefor alkenes, and -yneforalkynes. Thus, an alkane composed of six carbon atoms

in a chain is called hexane. An alkene with three carbonsis called propene.


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The Prefix: What Is Attached to the

Main Chain? The prefix indicates the name and location of each

branch and functional group on the main carbon chain.,

groups, attached to the main chain.

atom from an alkane. To name an alkyl group, changethe -ane suffix to -yl. For example, CH3 is the alkyl group

that is derived from methane, CH4. It is called the methylgroup, taken from the root meth-.


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ep n e roo : en y e onges c a n or r ng n

the hydrocarbon. If the hydrocarbon is an alkene or an

alk ne make sure that ou include an multi le bonds inthe main chain. Remember that the chain does not haveto be in a straight line. Count the number of carbon

.

Compound, add the prefix -cyclo- before the root. Ste 2 Find the suffix: If the h drocarbon is an alkane

use the suffix -ane. Use -ene if the hydrocarbon is analkene. Use -yne if the hydrocarbon is an alkyne. If more

,di- (2) or tri- (3) before the suffix to indicate the numberof multiple bonds.


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Step 3 Give a position number to every carbon atom inthe main chain. Start from the end that gives you the

bond, if there is one. If there is no double or triple bond,number the com ound so that the branches have the

lowest possible position numbers. Step 4 Find the prefix: Name each branch as an alkyl

group, and give it a position number. If more than onebranch is present, write the names of the branches ina p a e ca or er


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Step 4: Put the position number of any double or triplebonds afterthe position numbers and names of the

, . . Use the carbon atom with the lowestposition number toive the location of a double or tri le bond.

Ste 5 Put the name to ether: refix + root + suffix.


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ep raw e car on a oms o e ma n c a n. eave

space after each carbon atom for bonds and hydrogen

atoms to be added later. Number the carbon atoms. Step 2 Draw any single, double, or triple bonds between

the carbon atoms.

Step 3 Add the branches to the appropriate carbonatoms of the main chain.

forms a total of 4 bonds. Remember that double bonds

count as 2 bonds and triple bonds count as 3 bonds.


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- Both 2-propanol and ethanol contain the

same functional rou an OH h drox lgroup, as shown in the figure. Because

-

functional group, their behaviour is similar.


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e genera ormu a or a am y o s mp e

organic compounds is R+ functionalgroup. The letter Rstands for any alkylgroup. (If more than one alkyl group is

present, R and R3are also used.) For exam le the eneral formula ROH

refers to any of the following compounds:

CH3CH2CH2CH2OH, etc.


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rgan c compoun s are name accor ng

to their functional group. Generally, thesuffix of a compounds name indicates themost important functional group in the

molecule. For exam le the suffix -ene indicates the

presence of a double bond, and the suffix -

group.


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unc ona groups are a use u way o c ass y organ ccompounds, for two reasons:

.have similar physical properties. In the next two sections,you will learn to recognize various functional groups. Youw use unct ona groups to e p you pre ct t e p ys caproperties of compounds.

.chemically in very similar ways. Later, you will learn howcompounds with each functional group react.

C S B


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Compounds With Single-Bonded

Functional Groups Alcohols, alkyl halides, ethers, and amines

all have functional rou s with sin lebonds. These compounds have many

.

how to identify and name these,

intermolecular forces between their

molecules affect their properties and uses.


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An alcohol is an organic compound that

contains the OH functional rou . Depending on the position of the hydroxyl

, ,

secondary, or tertiary.


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ep oca e e onges c a n a con a ns an

group attached to one of the carbon atoms. Name the

arent alkane. Step 2 Replace the -e at the end of the name of the

parent alkane with -ol.

Step 3 Add a position number before the root of thename to indicate the location of the OH group.

hydrocarbon so that the hydroxyl group has the lowestpossible position number.) If there is more than one OHgroup, eave t e -e n t e name o t e parent a ane, anput the appropriate prefix (di-, tri-, or tetra-) before thesuffix -ol.


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Step 4 Name and number any other

branches on the main chain. Add thename of these branches to the prefix.

root + suffix.


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n a y a e a so nown as a a oa ane s an

alkane in which one or more hydrogen atoms have been

re laced with halo en atoms such as F Cl Br or I. Thefunctional group of alkyl halides is RX, where Xrepresents a halogen atom. Alkyl halides are similar in

, , .

To name an alkyl halide, first name the parenth drocarbon. Then use the refix fluoro- chloro- bromo-, or iodo-, with a position number, to indicate thepresence of a fluorine atom, chlorine atom, bromine

, ..


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20. Draw and name an alkyl halide that

has three carbon atoms and one iodineatom.

21. Draw and name a second, differentalkyl halide that matches the description in

Functional Groups


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Functional Groups

With the CO Bond A carbonyl group is composed of a carbon atom

doublebonded to an oxygen atom. In this section, you

compounds that have the CO group.

Aldehydes and ketones both have the carbonylfunctional rou . An aldeh de is an or anic com oundthat has a double-bonded oxygen on the last carbon of acarbon chain. The functional group for an aldehyde is


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When the carbonyl group occurs within a hydrocarbon

chain, the compound is a ketone. A ketone is an organic

-carbon within the carbon chain. The general formula for

a ketone is RCOR2 where R and R2 are alk l rou s

The functional group of a ketone is:


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Step 1 Name the parent alkane. Always

ive the carbon atom of the carbon lgroup the position number 1.

-

name of the parent alkane with -al. Thecarbonyl group is always given position

number 1. Therefore, you do not need toinclude a position number for it.


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ep ame e paren a ane. emem er a e

main chain must contain the CO group.

- ,end of the name of the parent alkane with -one. If thereis more than one ketone group, keep the -e suffix anda a su x suc as - one or -tr one.

Step 3 For carbon chains that have more than four,

group. Number the carbon chain so that the carbonylgroup has the lowest possible number


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car oxy c ac s an organ c

compound with the following functionalgroup:

This COOH group is called the carboxylgroup. The general formula for acarboxylic acid is RCOOH.


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Step 1 Name the parent alkane.

-name of the parent alkane with -oic acid.

tep e car on atom o t e car oxygroup is always given position number 1.

Name and number the branches that are


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Class01 ChemistryG12 Notes and Homework

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