Functional groups and Alkanes.notebook

Functional groups and Alkanes.notebook

1

September 28, 2016

Aug 13:23 PM

Functional Groups A group of atoms that has a characteristic chemical behavior in every molecule where it occurs

Aug 22:53 PM

Functional Groups Alkane (alkane, ending ane) all single bonded carbon

Alkene (alkene, ending ene) at least one double bonded carbon

Alkyne (alkyne, ending yne) at least one triple bonded carbon

Basic carbon backbone


2

September 28, 2016

Aug 22:55 PM

Functional Groups Aromatic hydrocarbon (arene)ring of carbons with resonating double bonds

alkyl halide (haloalkane, prefix) F, Cl, Br, I bonded to a carbon

Alcohol (alkanol, ending ol) HO is single bonded to a carbon

Aug 22:55 PM

Functional Groups Mercaptan (Thiol, ending thiol)Sulfurhydrogen group bonded to a carbon

Ether (ether, ending yl ether) Oxygen single bonded between two carbons

Carboxylic acid (Alkanoic acid, ending oic acid) carbon double bonded to one oxygen and single bonded to another oxygenhydrogen


3

September 28, 2016

Aug 22:55 PM

Functional Groups Ester (ester, ending yl oate) carbon double bonded to one oxygen and single bonded to another oxygencarbon

Ketone (alkanone, ending one) Double bonded oxygen to a carbon

Aldehyde (alkanal, ending al) carbon double bonded to an oxygen and a hydrogen

Aug 22:55 PM

Functional Groups Acid halide (acyl halide, ending oyl chloride) Carbon double bonded to oxygen and single bonded to chlorine

Nitro Compounds (nitro, prefix nitro) Nitrogen bonded to carbon and two oxygens

Amine (Amine, ending amine)Nitrogen bonded to at least one carbon.

Amide (amide, ending amide)Nitrogen bonded to a carbon=oxygen


4

September 28, 2016

Aug 1011:34 AM

Basic Naming We use the number of carbons in a straight (not really straight) chain to determine the parent name

Aug 41:20 PM

Alkane Simplest family of molecules that is comprised of carbons bonded by single bonds only.

General formula: CnH2n+2

Tetrahedral structure

Saturated: all carbons are bonded to the maximum number of hydrogen


5

September 28, 2016

Aug 41:20 PM

Alkane These are nonpolar molecules: > will only dissolve and dissolve in other

nonpolar substances > Low MP and BP (weak IMFs (LDFs)),

so commonly gases and liquids at room temp (more branches lowers boiling point)

> Low vapor pressure> Flammable

Aug 41:59 PM

Alkane Isomers"Same parts": Compounds with the same number and kinds of atoms but differ in the way the atoms are arranged

Types of Isomers:– Constitutional – Conformational*– Stereoisomers – Configurational


6

September 28, 2016

Aug 41:59 PM

Alkane Constitutional IsomersSame number and types of atoms but connected differently (not limited to alkanes)

Different compounds, with different properties, but same formula.

Types:

Carbon skeleton is different

Functional groups are different

Functional groups in a different location

Aug 157:53 AM

Warm up:Identify the functional groups in the following compound

Draw the structure for the following: Ethane, Octane, Hexane, and Butane


7

September 28, 2016

Aug 102:32 PM

Alkane Alkyl group (branches): Alkane groups on a carbon and are named using the number of carbons with the ending yl.

These groups can also contain functional groups (such as amine or alcohol).

Aug 103:44 PM

NamingPrefixLocantParentSuffix

Where and what are the substituents?

Where is the primary functional group?

How many carbons?

What is the primary functional group?


8

September 28, 2016

Aug 117:10 AM

NamingStep 1: Finding the parent hydrocarbon> Find the longest, continuous chain (not

always straight) of carbon atoms

> If there are two different chains of equal length, choose the one with the larger number of branches (less complex subsistent)

Aug 117:10 AM

NamingStep 2: Number the Carbon in the parent chain> Start numbering closest to the first branch

> If two branches are equidistance from the two carbons, then start number at the carbon with the closest second branch


9

September 28, 2016

Aug 117:10 AM

NamingStep 3: Identify and number the substituents> Assign a number (locant) to each

substitutuent

> If two branches are on the same carbon, they both get the same number

Aug 117:10 AM

NamingStep 4: Write the name as a single word> use hyphens to separate the different

prefixes and commas to separate numbers

> Cite multiple substituents in alphabetical order

> If two or more identical substituents are present, use a numeric prefix (di, tri, tetra, etc.)

3ethyl4,7dimethylnonane

4ethyl2,4dimethylhexane


10

September 28, 2016

Aug 117:10 AM

NamingStep 5: Name complex substituents as its own compound> This is for complex branches when

necessary (alkyl branches)

2,3dimethyl6(2methylpropyl)decane

or

6isobutyl2,3dimethyldecane

Aug 117:10 AM

NamingPractice:


11

September 28, 2016

Aug 117:10 AM

Naming1. Using skeletal structures, draw out all of the isomers of heptane. How many are there? Be sure that each structure is unique.

2. Under each structure, write the correct IUPAC name. Watch your numbers, commas, and hyphens.

3. What are the formulae for these isomers?

4. How many isomers are there for octane?

Aug 1610:51 AM


12

September 28, 2016

Aug 1610:51 AM

Aug 117:10 AM

NamingAlkyl Halide

1. Find the parent hydrocarbon

2. Number the atoms

3. Identify and number the substituents

4. Write name as single word

Fluorine > Fluoro Chlorine > Chloro

Bromine > Bromo Iodine > Iodo

1chloro3ethyl4fluorohexane


13

September 28, 2016

Aug 139:46 AM

Naming

Aug 139:46 AM

NamingDrawing the structure from the name2methylheptane

4ethyl3,4dimethyloctane

2chloro3,3diethyl6methylnonane

4ethyl2,2dimethylhexane

4isopropyl3methylheptane

1,3difluoro3methylpentane


14

September 28, 2016

Aug 227:48 AM

Warm up:

Cl

1. Name the compound to the left

2. Define constitutional isomer

3. Give the line structure and name for a constitutional isomer for the compound on the left

4. Give the proper IUPAC name for the functional group present in the compound on the left

Aug 1310:40 AM

Conformational IsomersRemember an isomer is when two compounds share the same chemical formula (CxHy...)

Stereochemistry: The branch of chemistry concerned with the 3D aspects of molecules

Often crucial for determining properties and biological behaviors of organic molecules

Due to the σ bonding of a single bond, rotation can occur in openchange


15

September 28, 2016

Aug 1310:40 AM

Conformational IsomersDue to the σ bonding of a single bond, rotation can occur around the CC bond in openchain molecules

Conformational isomers (Conformers): Molecules with different arrangement of atoms due to bond rotation

Cannot be isolated due to rapid interconversions

Conformations: different arrangements of atoms due to bond rotation

Aug 1310:40 AM

Conformational IsomersRepresentations of conformational isomers

Sawhorse Newman Projection

Eclipsed

Staggered

Potential energy comparison for each conformation? (this is called a torsional barrier!)


16

September 28, 2016

Aug 213:24 PM

Conformational Isomers

12kJ/mol or 2.9kcal/mol PE difference 4 kJ/mol per each interaction

Minimum energy occurs in staggered and maximum occurs in eclipsed, why?

Conformations of Ethane

Torsional strain: Energy present due to the interaction between CH orbitals on one carbon with orbitals on the adjacent carbon

Aug 213:24 PM

Conformational Isomers14kJ/mol or 2.9kcal/mol PE difference 4 kJ/mol per Hydrogenhydrogen interaction, 6 kJ/mol per methylhydrogen interaction, why the difference?

Conformations of propane


17

September 28, 2016

Aug 213:24 PM

Conformational IsomersConformations of Butane things get a bit more complicated!

Anticonformation Gauche conformation

Steric Strain: The repulsive interactions that occurs when atoms are forced closer together than their atomic radii allow (seen in the Gauche conformation! )

Aug 213:24 PM

Conformational IsomersConformations of Alkanes


18

September 28, 2016

Aug 213:24 PM

Conformational IsomersConformations of AlkanesFor 2methylpropane (isobutane). Sighting along the C2C1 bond

Draw a Newman projection of the most stable conformation

Draw a Newman projection of the least stable conformation

Make a graph of energy versus angle of rotation around the C2C1 bond

Since an H<>H eclipsing interaction costs 4.0 kJ/mol and an H<>CH3 eclipsing interaction costs 6.0 kJ/mol, assign relative values to the maxima and minima in your graph

Aug 213:42 PM

CycloalkanesAlicylic: Closed alkane Rings

Most organic compounds contain rings of carbon atoms (I.E. Proteins, lipids, carbohydrates, and nucleic acids.


19

September 28, 2016

Aug 213:42 PM

CycloalkanesPropertiesunsaturated

nonpolar and fairly inert (just like alkanes)

less flexible than openchain alkanes

Less freedom in rotation (conformations)

Aug 213:42 PM

CycloalkanesNamingChemical formula: CnH2n

Why?

Naming:


20

September 28, 2016

Aug 213:42 PM

CycloalkanesNamingStep 1: Find the parentThis is still the longest chain of carbons! If the ring is equal or larger than the free chain, then the chain is named as a substituent and the ring is the parent. If the ring is smaller than the chain, than the chain is the parent and the ring is the substituent

Methylcyclopentane 1cyclopropylbutane

Aug 213:42 PM

CycloalkanesNamingStep 2: number the substituents and name Number the chain so that the substituents have the lowest number possible. Start at one of the substituents. If two substituents could receive the same number, start numbering in alphabetical order.

1,3dimethylcyclohexane vs 1,5dimethylcyclohexane

2ethyl1,4dimethylcycloheptane vs.

1ethyl2,6dimethylcycloheptane

3ethyl1,4dimetylcycloheptane

1ethyl2methylcyclopentane vs 2ethyl1methylcyclopentane


21

September 28, 2016

Aug 213:42 PM

CycloalkanesNamingCisTrans isomerism Cycloalkanes do not have the same rotational freedom as an open chain alkane, therefore they have two faces as viewed edgeon: "top" face and "Bottom" face

This allows for isomerism

Aug 213:42 PM

CycloalkanesNamingCisTrans isomerism

1,2dimethylcyclopropane

Stereoisomers (Configurational isomers): Same connection, but different 3D geometry

CisTrans isomers: Subclass of stereoisomers


22

September 28, 2016

Aug 213:42 PM

CycloalkanesNaming

H

H

CH3

ClH

H3C CH2CH3

H

Sep 610:29 AM


23

September 28, 2016

Aug 213:42 PM

CycloalkanesStability Torsion Strain: The unfavorable Coulombic interactions between two groups

Steric Strain (Steric Hindrance: The unfavorable Coulombic interactions between two groups "running into each other" or being closer together than their nuclei allow.

HH eclipsed > Torsion

HCH3 eclipsed > Mostly torsion

CH3CH3 eclipsed > Torsion and Steric

CH3CH3 gauche > Steric

Aug 213:42 PM

CycloalkanesStability Angle Strain: The strain induced in a molecule when bond angles are forced to deviate from the ideal 109° tetrahedral value.


24

September 28, 2016

Aug 213:42 PM

CycloalkanesStability This strain causes the molecule to have a higher potential energy. This increased potential energy can be measured through the heat of combustion

Notice cyclopentane is significantly lower than cyclopropane and cyclobutane, and cyclohexane is strain free, why?

Aug 213:42 PM

CycloalkanesStability

Angle Strain The increased potential energy due to the bond angles differing from the ideal tetrahedral bond angle.

Puckered 3D conformations When a cycloalkanes 3D structure is not flat (on one plane)


25

September 28, 2016

Aug 213:42 PM

CycloalkanesStabilityCyclopropane This is the most strained of all rings, primarily due to the 60° bond angles and a considerable amount of torsional strain

Cyclopropane has bent bonds in order to achieve the deviation from the ideal 109.5° bond angles to form 60° bond angles. These bonds are weaker and more reactive than typical alkane bonds

Aug 213:42 PM

CycloalkanesStabilityCyclobutaneCyclobutane has less angle strain than cyclopropane, but has more torsional strain due to the larger number of ring hydrogens. This results in both compounds have similar total strain.

One carbon lies about 25° degrees above the plane (puckered) which increases angle strain, but decreases torsional strain. The two opposing effects achieve a minimumenergy balance


26

September 28, 2016

Aug 213:42 PM

CycloalkanesStabilityCyclopentaneCyclopentane has a puckered, nonplaner conformation that balances the angle strain and torsional strain.

One carbon lies out of the plane while the other four are approximately in the same plane. This results in most of the hydrogens being nearly staggered

Aug 213:42 PM

CycloalkanesStabilityCyclohexaneMost common cycloalkane. Found widely in nature and can be found in compound such as steroids, pharmaceuticals, and flavoring agents.

Chair

Two conformations of cyclohexane:

Boat


27

September 28, 2016

Aug 213:42 PM

CycloalkanesStabilityCyclohexane Chair ConformationThis conformation is strain free due to not having any angle strain or torsional strain

Aug 213:42 PM

CycloalkanesStabilityCyclohexane Boat ConformationThis conformation is nearly free of angle strain, but does have steric and torsional strain. This conformation has more potential energy, and is therefore only adopted under special circumstances.


28

September 28, 2016

Aug 213:42 PM

CycloalkanesCyclohexaneaxial and equatorial bonds The chair conformation affects the chemical behavior of many cyclohexane based molecules.

The conformation also has two types of positions for substituents

Axial: Perpendicular to the ring, parallel to the ring axis (6 positions)

Equatorial: plane to the ring, around the ring equator (6 positions)

This is NOT the same as cis and trans! any two substituents on the same face of the ring are cis, regardless of axial or equatorial and regardless of whether they are adjacent. Substituents on the opposite faces are always trans.

Aug 213:42 PM

CycloalkanesCyclohexaneaxial and equatorial bondsConformationally Mobile: Different chair conformations readily interconvert, exchanging axial and equatorial positions at room temperature.

Ringflip: The interconversion between axial and equatorial positions.

Therefore, axial and equatorial positions do not result in isomeric forms of monosubstituted cyclohexanes


29

September 28, 2016

Aug 213:42 PM

CycloalkanesCyclohexanemonosubstituted ConformationsEven though the chair conformations rapidly flip at room temp, the two conformations are not always equal in stability.

Methylcyclohexane

1,3diaxial interaction: Steric strain between substituents/hydrogens in the 1, 3, and 5 position.

Aug 213:42 PM

CycloalkanesCyclohexanedisubstituted ConformationsIn monosubstituted cyclohexane, the equatorial substituent is the most stable chair conformation.

cis1,2dimethylcyclohexane and

trans1,2dimethylcyclohexane

Documents

Functional groups and Alkanes.notebook