KLLULIAM

=__** ALKANES **__=

PROPERTIES OF ALKANES 1. Define what is meant by "homologous series". Describe their features in terms of physical and chemical properties. 2. PREDICT and EXPLAIN the trends in boiling points of members of a homologous series (from C1-C6) 3. Define what is meant by "isomer". Give an example of a set of isomers. 4. PREDICT and EXPLAIN the trend in boiling points of isomers. Using the examples from #3, arrange the boiling points in increasing/ decreasing order.

REACTIONS OF ALKANES Introduction: Comment on the reactivity of alkanes. (high or low?) Explain your answer.

Specific reactions: For this part, make sure to highlight the chemical equations (focusing on a sample reactant, the products they will produce, and catalyst, if present) 1. COMBUSTION (complete and incomplete) 2. REACTION OF ALKANES WITH CHLORINE AND BROMINE

PROPERTIES OF ALKANES
A homologous series is one in which all the members have the same general formula. The neighboring members of the series differ by -CH2-, and they show similar chemical properties and a gradation in their physical properties. The homologous series of alkanes all follow the general formula CnH2n+n.

The all have similar chemical properties, however the physical properties gradually increases. For instance, boiling point, a physical property, gradually increases as the molecules get bigger because, ultimately, more energy is needed to pull the molecules apart. Following that rule, ethane will have a higher boiling point as compared to methane because more energy, in the form of heat, will be needed to break the molecules of ethane apart.



The first four alkanes are gases at room temperature and pressure, however, the fifth member, pentane, is a liquid. As the number of carbons continue to rise so does the boiling point. When the value of carbon reaches around 20, the alkanes become solid at room temperature.

Their boiling points are very low considering their molar mass. The reason for this is because the electronegativity values for carbon and hydrogen are very similar, and so the molecules are either completely non-polar because of their symmetrical shape or have very low polarity.

Note: Different structural isomers will have different boiling points, For example, the three isomers of pentane have boiling points ranging between 9.5C and 36.3C.

STRUCTURAL ISOMERS
When two or more compounds have the same molecular formula but a different structural formula they are known as structural isomers. The molecular formula C5H12 can have three different structural isomers.

Note: Different structural isomers will have different boiling points, For example, the three isomers of pentane have boiling points ranging between 9.5C and 36.3C.

pentane: b.p. +36.3C 2-methyllbutane: b.p. +27.9C 2, 2-dimethyllpropane: b.p. +9.5C

**REACTIVITY**
Basically, alkanes have low reactivity. A reason for this is because their old name was parrafins, which means "little activity." This is mainly because of the strong carbon-to-carbon and carbon-to-hydrogen bonds that cannot be easily broken, and although they react pretty well with halogens and burn well too, they cannot expand to form octets, making alkanes more stable.

Their combustion reactions are very exothermic, which means the formation of stronger carbon-to-oxygen double bonds (ex. carbon dioxide, CO2) or oxygen-to-hydrogen bonds (ex. water, H2O).

**SPECIFIC REACTIONS**
1. a. Complete Combustion - it is the rapid chemical reaction of a substance with oxygen or O2 For example, this is the complete combustion of octane: 2C8H18 + 25O2 --> 16CO2 + 18H2O

b. Incomplete Combustion - undergone when there is a lack of oxygen for complete combustion - products of this reaction include carbon monoxide, carbon dioxide, carbon, and water For example, a possible equation for a reaction involving the incomplete combustion of octane is: C8H18 + 9O2--> C+ 5CO + 2CO2 + 9H2O

2. Reaction of Alkanes with Chlorine and Bromine Steps: 1. Initiation step: involves the formation of free radicals, is the reason that the reaction occurs only in the presence of ultraviolet light *UV light has enough energy to break the chlorine to chlorine bond homolytically. 2. It forms free radicals. Free radicals contain an unpaired electron in one of their orbitals, and they are highly energetic and reactive.

=__** ALKENES **__=

Properties of alkenes:  What are their similarities and differences with alkanes? Between the two groups, which is saturated and unsaturated? How can you tell?

 Reactions of alkenes:  Write equations showing the reactants, products (give the general name of the products formed) and conditions/ catalysts used for each reaction:  1. combustion  2. hydrogenation  3. halogenation (producing a monosubstituted product)  4. halogenation (producing a disubstituted product)  5. hydration  6. polymerization

Properties of Alkenes
Alkenes contain a carbon-to-carbon double bond and form a homologous series with the general formula CnH2n. The simplest alkene is ethene, C2H4. Alkenes are named by taking the longest carbon chain and the specifying where the double bond begins:

ex. but-1-ene

The physical properties of alkenes are similar to those of alkanes (either non-polar or have very low polarity). Like alkanes, they have low boiling points, which increase in the same trend as with alkanes, and alkenes are insoluble in polar solvents.

Alkenes burn in extra oxygen to give carbon dioxide and water as products of complete combustion.

Because of the presence of double bonds, chemical properties are quite different with that of alkanes.

Lastly, alkenes are said to be unsaturated because they can undergo addition reactions across double bonds. When this happens, the product is saturated because both carbon atoms will then have four single bonds to other atoms and no further addition can occur.

ex. Addition reaction of ethene

1. Combustion
Combustion it is the rapid chemical reaction of a substance with oxygen or O2 example: C2H4(g) + 3O2(g) > 2CO2(g) + 2H2O(g) Ethylene+Oxygen > Carbon dioxide+ Water

2. Hydrogenation

Hydrogen will add to Alkenes if nickel is present at 180 degrees celsius. Products will be the corresponding alkane. example:

C2H4+H2 + (Ni @ 180 degrees celsius) -> C2H6

Ethene+ Hydrogen (with presence of Nickel at 180 degrees celsius) > Ethane

3. Halogenation (monosubstituted product) Hydrogen Halides such as hydrogen chloride and hydrogen bromide react readily with alkenes to form the addition product. example: Ethene reacts with hydrogen chloride to form chloroethene.

C2H4+ HCI > C2H5Cl

4.) Halogenation -Alkenes react with halogens, such as chlorine, bromine and iodine, to produce a disubstituted product.

Example: C2H4 + Br2 --> C2H4Br2 Ethene + Bromine --> 1,2 - dibromoethane or ethylene dibromide *They react at room temperature.*



5.) Hydration -Water doesn't react with alkenes under normal conditions.  -When sulfuric acid is used, however, a hydrogen sulfate addition product is formed.  -The water can then be added to the carbon-carbon double bond, forming in an alcohol and recovering the sulfuric acid.

Example: C2H4 + H2SO4 --> C2H6O4S ---(H2O)--> C2H5OH + H2SO4 Ethene + Sulfuric acid --> Ethyl hydrogensulfate --(water)--> Ethanol + Sulfuric Acid

6.) Polymerization -Alkenes can react with each other under certain conditions.  -Products are addition polymers.  -This happens when units of the same type of alkene, like chloroethene or phenylethene, bond.

Examples: nC2H3Cl --> (C2H3Cl)n Chloroethene monomer --> poly(chloroethene) *n is the number of alkene units. In this case, it is the number of chloroethene units*

nC8H8 --> (C8H8)n Phenylethene monomer --> poly(phenylethene)


 * Chloroethene monomer --> poly(chloroethene)

=Organic Derivatives=

1.) Alcohols General formula: R-OH Naming: The -e at the end of the alkane is replaced by -ol. <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">Examples: <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">CH3OH-Methanol <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">C2H5OH-Ethanol <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">C3H7OH- 1-propanol <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">CH3CH(OH)CH3- 2-propanol <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">C(CH3)3OH-2-methyl-2-propanol

<span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">Kinds of Alcohols <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">Carbon atom part of the -OH group is bonded to one alkyl group (CHn), but with the exception of methanol <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">The carbon atom that is connected with the -OH is bonded to 2 alkyl groups. <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">Carbon atom that is part of -OH is connected to 3 alkyl groups
 * 1) <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px;">Primary
 * 1) <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px;">Secondary
 * 1) <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px;">Tertiary

<span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">Properties <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">Hydrogen bond is present (between Oxygen and Hydrogen) <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">High Boiling Points <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">Soluble in water; solubility decreases as parent chain becomes longer <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">Polar Substance <span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">Acidic

<span style="font: normal normal normal 12px/normal Helvetica; letter-spacing: 0px; margin: 0px;">Reactions <span style="font: normal normal normal 13px/normal Arial; letter-spacing: 0px; margin: 0px;">All alcohols burn readily in plentiful supply of oxygen to form carbon dioxide and water. Produces heat when Oxygen is added to the Alcohol
 * 1)  Combustion- is the rapid chemical reaction of a substance with oxygen or O2

<span style="font: normal normal normal 13px/normal Arial; letter-spacing: 0px; margin: 0px;">Sample Reactions: <span style="font: normal normal normal 13px/normal Arial; letter-spacing: 0px; margin: 0px;">C2H5OH+3O2—>2CO2+3H20

<span style="font: normal normal normal 13px/normal Arial; letter-spacing: 0px; margin: 0px;"> 2.Oxidation-Losing electrons by giving it off

<span style="font: normal normal normal 13px/normal Arial; letter-spacing: 0px; margin: 0px;">Oxidizing Agent is the compound in the reaction that gains electrons

<span style="font: normal normal normal 13px/normal Arial; letter-spacing: 0px; margin: 0px;">a.Primary Alcohols <span style="font: normal normal normal 13px/normal Arial; letter-spacing: 0px; margin: 0px;">can be oxidized into either an aldehyde or carbon

2.) Ketones

- General formula: R-COR` (R` represents the same alkyl group as R or a different alkyl group) - Naming: The -e on the end of the longest chain alkane is replaced by -one (Example: propane --> propanone) - Properties: dipole-dipole force, moderate boiling point, soluble in water, moderate volatility, polar, acidic



3.) Amines

- General formula: R-NH 2 - Properties: hydrogen bond (primary and secondary) or dipole-dipole force (tertiary), high (primary and secondary) or moderately low (tertiary) boiling point, soluble in water, low (primary and secondary) or moderately high (tertiary) volatility, polar, basic

Kinds of Amines: 1.) Primary amines - Naming: NH 2 is attached to the parent chain. There are many variations in naming, but the simplest way is to add "amino" before the parent chain name (Example: 1-aminopropane)



2.) Secondary amines - Naming: N-H is attached to two of the same kind of alkyl group. Use di- as its prefix, name the alkyl group in which the N-H is attached to, and end the name with -amine (Example: dimethylamine, diethylamine)



3.) Tertiary amines -Naming: Like secondary amines, N is attached to three of the same kind of alkyl group. Instead of using di- as a prefix, tri- is used (Example: trimethylamine)



<span style="font-family: Arial,Verdana,Helvetica,sans-serif; font-size: 16px; line-height: normal;">Sources: <span style="font-family: arial,helvetica,sans-serif; font-size: 13px; line-height: 19px;">Neuss, G. (2007). IB Diploma Programme Chemistry Course Companion http://www.chemguide.co.uk/organicprops/alkenes/hydration.html#top http://www.chemguide.co.uk/organicprops/alkenes/polymerisation.html#top http://www.chemguide.co.uk/organicprops/alkenes/halogenation.html http://www.docbrown.info/page04/OilProducts/PVCform.gif http://www.chemistryrules.me.uk/junior/ethene_bromination.gif http://www.chemguide.co.uk/organicprops/carbonyls/background.html http://www.chemguide.co.uk/organicprops/amines/background.html http://upload.wikimedia.org/wikipedia/commons/4/48/Ketone-general.png