PORG Q1 (MIDTERM): Physicochemical properties

physical property

• A property that does not affect the chemical identity of a compound

•Can be observed and measured without changing a compound's composition of matter

-Any substance that has mass and can occupy space

Intrinsic

Qualitative (cannot count)

Ex. Boiling and melting point, color

physical property

• A property that does not affect the chemical identity of a compound

•Can be observed and measured without changing a compound's composition of matter

-Any substance that has mass and can occupy space

Intrinsic

Qualitative (cannot count)

Ex. Boiling and melting point, color

Extrinsic

Quantitative ( can count)

Ex. Mass, length, radius, etc

intramolecular forces

Within atoms, connected by actual bonds

- Ionic

- Covalent (weakest)

- metallic (strongest)

Different types of forces in INTRAmolecular forces

intermolecular forces

Within molecules, connected by attraction/ repulsion

(AFFECT THE PHYSICAL PROPERTIES OF SUBSTANCE)

• The physical properties of molecules are in part dependent on the type's of ______ present.

•Boiling points (BP) are dependent on the mass of the molecule.

•Solubility, the ability to dissolve into a solvent, is dependent on IMFs.

•The strength of the interaction between molecules is also dependent on the overall shape of the molecule.

- van der Waals (weakest)

- Ion dipole

- hydrogen bond (strongest)

Common types pf intermolecular forces

Keesom

Debye

London dispersion (weakest)

3 main type (/subtype) of van der waals

Keesom

Strongest in van der waals

dipole-dipole

Keesom

dipole interaction

Dipole-dipole

Polar-polar

Keesom other names

dipole-induced dipole

Debye

induce dipole-induce dipole

London dispersion

1)Hydrogen bonding

2)Dipole-dipole

3)London Dispersion

3 types of IMFs, by decreasing strength they are:

Hydrogen bond

H connects to F,O,N

Can found in DNA

Hydrogen Bonding

complex interaction that includes dipole-dipole, as well as orbital interactions and the transfer of electron density between molecules.

-These are the strongest of the IMFs and range from 5 - 25 kJ/mol

electronegative

In hydrogen bonding the more _______ the atom the stronger the interaction.

(The atom H is attached to usually has a lone pair of e-)

dipole-dipole

attractions between oppositely charged regions of polar molecules (Positive-negative attraction)

forces arise from the attraction of oppositely charged atoms (other than H) in molecules.

These molecules may have a permanent dipole moment. Generally in organic molecules they result from the presence of C-X bonds where X is more electronegative to that of C.

-These are generally weaker than H-bonding, ranging from about 5-10 kJ/mol.

Induced

Influence/ initiate to do something

causing a reaction or effect to occur

London Dispersion

forces arise from the movement of electrons within a molecule.

This natural motion can produce an uneven distribution of the electrons (polarization of the distribution) resulting in a temporary dipole moment in the molecule.

This will induce the movement of electrons in adjacent molecules producing a dipole moment in them.

These "induced" dipole moments are very brief as they disappear when the electrons move to new locations within the molecule, so they forces are weak 2-5 kj/mol

- Structure of Functional Group

- Molecules having a polar functional group have a higher boiling and melting point

- non polar low boiling point

Factors Affecting the Physical Properties of Organic Compounds

higher molecular masses

Melting, boiling point and density

•Molecules with __________ have higher _______, _______, and ______ and density

Higher molecular masses

🡺 Large molecular sizes

🡺 Stronger London dispersion forces among molecules

branched chain

Molecules with _______ chains

🡺 b.p. and density lower than its straight-chain isomer

Straight-chain isomers have greater surface area in contact with each other

🡺 Greater attractive force among the molecules

larger molecules

higher boiling and melting point

Length of Carbon Chains

As a rule, _________ molecules have _________ boiling (and melting) points.

Solubility

Ability of solute to be soluble

If the solvent is polar, like water, then a smaller hydrocarbon component and/or more charged, hydrogen bonding, and other polar groups will tend to increase the _________.

More carbons

More ______ means more of a non-polar/hydrophobic character, and thus lower solubility in water.

charged group

Anything with a _____ (eg. ammonium, carboxylate, phosphate) is water soluble

alcohols, amines

Any functional group that can donate a hydrogen bond to water (eg. _____,______) will significantly contribute to water solubility.

ketones, aldehydes, ethers

Any functional group that can only accept a hydrogen bond from water (eg. _____,_____,_____) will have a somewhat smaller but still significant effect on water solubility.

alkyl halides, thiols, sulfides

Other groups that contribute to polarity (eg. _______,______,_____) will make a small contribution to water solubility.

Boiling and melting point

processes in which noncovalent interactions between identical molecules in a pure sample are disrupted.

stronger the noncovalent interactions, the more energy that is required, in the form of heat, to break them apart.

homologous series

The boiling points of the compounds in any _________ series increase as their molecular weights increase because of the increase in van der Waals forces.

Branching

a compound lowers its boiling point because it reduces the area of contact.

chemical reaction

occurs when one substance is converted into another substance(s).

accompanied by breaking of some bonds and by making of some others.

Reaction Mechanism

detailed knowledge of the steps involved in a process in which the reactant molecules change into products

bond fission/ breakage

The breaking of a covalent bond is known as

During ____ the two shared electrons can be distributed equally or unequally between the two bonded atoms.

Homolytic Fission

fission of covalent bond with equal sharing of bonding electrons

Free radicals

neutral but reactive species having an unpaired electron and these can also initiate a chemical reaction.

Heterolytic fission

fission of a covalent bond involving unequal sharing of bonding electrons.

ions

This type of bond fission results in the formation of _____.

carbonium ion or carbocation

The ion which has a positive charge on the carbon atom, is known as the _______.

carbanion

ion with a negative charge on the carbon atom is known as the ______.

Electrophiles and Nucleophiles

The charged species obtained by the heterolytic fission initiate chemical reactions and they are classified as

Electrophiles

electron deficient species and it may be positively charged or neutral.

Nucleophiles

negatively charged or electron rich neutral species

substution

reaction involves the displacement of one atom or group in a molecule by another atom or group

nucleophilic substitution reactions.

Aliphatic compounds undergo ______

electrophilic

substitution reaction which takes place in an aromatic hydrocarbons

_______ reagent attacks the aromatic ring because the latter is electron rich. The leaving group, in this case, is always one of the hydrogen atom of the ring.

Elimination

characterized by the removal of a small molecule from adjacent carbon atoms and the formation of a double bond

Addition

Unsaturated hydrocarbons such as alkenes and alkynes are extremely reactive towards a wide variety of reagents. The carbon-carbon double bond (-C=C-) of an alkene contains two types of bonds. In alkynes, three carbon-carbon bonds.

Molecular Rearrangements

proceeds with a fundamental change in the hydrocarbon skeleton of the molecule.

During this reaction, an atom or group migrates from one position to another