Organic Chemistry Exam #1 chapters 1-4

what is organic chemistry?

Study of carbon compounds

why is carbon special?

-Carbon is a group 4a element

-four valence electron

-4 covalent bonds

-90% of 30+ million known chemical compounds contain carbon

Torben Bergman(1770)

distinguished organic from inorganic chemistry. Early scientist, believe organic compounds required a vital force.

Chevreul (1816)

demonstrated that organic substances could be prepared from nonliving materials.

Wöhler (1828)

converted ammonium cyanate to urea, helping disprove the vital force idea.

proton

Positively charged and located on the nucleus

neutron

Neutrally charged and located on the nucleus.

electron

negatively charged, and in the electron cloud around the nucleus.

atomic Number (Z)

Number of protons

mass number (A)

Proton+ Neutrons

isotopes

same element→ Same number of protons, but different number of neutrons.

atomic mass (amu)

Weighted average of naturally occurring isotopes.

if an atom has six protons and six neutrons then

Atomic Number=6

Mass number = 12

quantum mechanics

describes where electrons are likely to be found

S orbital

spherical

P orbital

dumbbell shaped

d orbital

More complicated/elongated dumbbell shaped

F orbital

Also exist, but is less important for introductory organic chemistry.

The first shell in an orbital

1s; maximum 2e-

2nd shell orbital

2s+three 2p; maximum 8e-

3rd orbital

3s+three 3p + five 3d;maximum 18e-

Aufbau Principle

electrons fill the lowest energy orbitals first.

1s→2s→2p→3s→3p→4s→3d

Pauli Exclusion Principle

maximum of two electrons per orbital and MUST HAVE opposite spins.

Hunds Rule

when equal – energy orbitals are available:

-One electron in each orbital first

why do atoms form bonds?

Atoms form bonds because the resulting compound is more stable than the separate atoms.

Ionic Bond

electrons are transferred,and common in salts.

covalent bond

Electrons are shared, especially IMPORTANT in organic chemistry.

Lewis structure

Represents valence electrons as dots

non-bonding electrons=

lone– Pair electrons

valence bond theory

Electrons pair and overlapping orbitals, and also the electrons are attracted to both nuclei.

Sigma Bond

forms through head on overlap.

Single bonds or sigma bonds

Circular/cylindrical cross-section

Bond energy

Measures the strength associated with breaking/forming a bond.

Bond Length

1.) Too close→ Nuclei repel

2.) Too far apart→ Bonding becomes weak

oxygen in water

sp³ orbital

molecular orbital theory

Describes where electrons are likely to be found in a molecule.

two types of molecular orbital

Antibonding MO, and Bonding MO.

bonding MO

Lower energy and more stable

anti-bonding MO

higher energy and less stable

drawing organic structures-line – angle structures three rules

1.) carbon atoms aren’t usually shown

2.) hydrogen attached to carbon aren’t shown

3.) Atoms other than C and H are shown

electronegavity

atoms ability to attract shared electrons in covalent bond.

f=4.0

most electronegative

Cs=0.7

least electronegative

how to see electronegatively.

generally increases toward the upper-right

inductive effect

shifting of electrons in a bond because of the electronegativity of nearby atoms.

similar electronegativity

Nonpolar covalent

electronegativity difference <2

Polar covalent

electronegative difference >2

Ionic

A molecule can have polar bonds, but still be

Non-polar overall

Dipole moment

μ = Q × r

symmetry can cause apples to cancel? True or false.

True

formal charges

Help keep track of valence electrons in molecules

resonance forms

differ only in the location of pi electrons or loan pairs. Connected by a double headed arrow

curved arrow

Movement of an electron pair

Arrow tail

Where electrons start

arrowhead

where electrons go

Bronstad acid

Donates H +

bronsted base

accept H+

Ka

acidity Constant

Large Ka

strong acid

Small Ka

weak acid

Lower pKa

stronger acid

Higher pKa

weaker acid

The reaction tends to favor the side with the

Weaker acid

If you have:

Acid A + Base B ⇌ Base A + Acid B

compare the pKa Values of the acids

organic acids contain a

Positively polarized hydrogen

Two important types:

O-H acids

C-H acids

iorganic base has an atom containing a lone pair of electrons that can bond to H+. True or False?

True

Lewis acid

electron – pair accepter

Lewis base

Electron-pair Donor

organic chemistry happens in

3-D space

non-covalent interactions (Three major types)

1.) dipole-dipole forces

2.) dispersion forces

3.) Hydrogen bonds

dipole-dipole

Between polar molecules because of electrostatic interactions between dipoles.

dispersion forces

occur between all neighboring molecules.

hydrogen bond

H bonded to an electronegative atom.

functional group

A collection of atoms at a specific site in a molecule that gives the molecule characteristic behavior.

alkene

C=C double bond

alkyne

c///c triple bond

arene

special bonding represented by alternating single/double bonds, in a six membered ring.

alkanes

compounds containing:

•C-C bonds

•C-H bonds

•no functional group

alkanes are also called

aliphatic compounds

isomer

compounds or isomers when they have the same molecular formula but different arrangements of their atoms.

constitutional isomers

differ and how their atoms are connected/arranged in chains.

straight-chain/normal alkane

carbons are connected to no more than two other carbons

branched-chain alkane

at least one carbon is connected to three or four carbons

condensed structure

Shorten way to represent a molecule.

EXAMPLE

CH₃CH₂CH₂CH₃

=butane

alkyl group

formed by removing 1 H from an alkane.

alkyl group general abbreviation

R

the alkane ending in -ane changes to -yl

EXAMPLE

methane→ Methyl-CH3

types of alkyl groups

primary, secondary, and tertiary.

primary (1)

connecting carbon is attached to one other carbon

secondary (2)

connecting carbon is attached to two other carbons

tertiary (3)

Connecting carbon is attached to three other carbons.

Remember for classifying alkyl groups

based on the carbon attached to the rest of the molecule, NOT simply the number of carbons in the entire group.

naming alkanes

1. find the parent chain

2. Number the parent chain

3. Identify substituents

4. write the name

1 Carbon

methane

2 Carbon

Ethane

3 Carbon

propane

4 Carbon

Butane

5 Carbon

Pentane

6 Carbon

Hexane