Presentation on theme: "SCH4U Properties of Organic Compounds. Intermolecular Forces and Physical Properties ● Can the molecules form hydrogen bonds? ○ If hydrogen bonds can."— Presentation transcript:
Intermolecular Forces and Physical Properties ● Can the molecules form hydrogen bonds? ○ If hydrogen bonds can form and they have a high BP. ○ Small molecules are soluble in water. Long chains exhibit the properties of the parent hydrocarbon and are insoluble in water. ● Are the molecules polar? ○ If it is polar then the BP is higher than a similar non-polar molecule. Also, if it is polar and can form hydrogen bonds then the BP increases dramatically. ○ As the non-polar carbon backbone gets longer the molecules starts to loose the properties associated with polarity. Long chains exhibit the properties of the parent hydrocarbon. ● How strong are the dispersion forces? ○ The larger the molecule the more electrons it has and the stronger the dispersion forces. ○ If the molecule has an irregular shape then it will have a lower BP and solubility than a similar molecule with a regular pattern since they can pack closer to each other.
Intermolecular Forces and Physical Properties ● Nonpolar molecule: ○ London dispersion forces only and the longer the chain the higher the boiling point. Also, they are non polar and are only soluble in nonpolar solvents (insoluble in water). ● Polar molecule: ○ London dispersion forces and dipole bonds therefore have a higher BP than similar non-polar molecules. Short chains soluble in water but as the backbone gets longer it loses its polar nature and acts like a similar non polar molecules. ● Polar molecules that form hydrogen bonds: ○ London dispersion forces, dipole bonds, and hydrogen bonds therefore have a very high BP than a similar non-polar or polar molecule. If only one HB then, short chains soluble in water but as the backbone gets longer it loses its polar nature and acts like a similar non-polar molecules.
ALKANES Properties: -Hydrophobic (does not mix with water and other polar substances) -Generally low boiling points (due to weak London Dispersion Forces) - Longer alkane molecules have higher boiling points
Properties: -Are hydrophobic like all hydrocarbons -terminal alkenes (ex. ) have slightly lower boiling points than their alkane counterparts, but cis, trans, and cyclic alkenes have slightly higher boiling points. ALKENES
Properties: -cis and trans alkenes have slightly higher boiling points than their alkane counterparts -this is due to their increased ability to stack together and form London Dispersion Forces (cis generally stacks better and has higher boiling points) cistrans
ALKYNES Properties: -Are hydrophobic like all hydrocarbons -Have higher boiling points than alkanes and alkenes due to their ability to stack
Symbols and Functional Groups ● alkyl group → R, R', R" ● halogen atom (Cl) → X ● phenyl group → Ø ● Memorize ○ Table 1.4 on page 22
Definition of an Alcohol An alcohol is an organic compound that contains the –OH functional group, which is called the hydroxyl group. Ethanol – used in alcoholic beverages Methanol – auto antifreeze and/or mouthwash (yikes!) isopropanol – antiseptic
Naming Alcohols The root name is based on the longest chain with the -OH attached. The chain is numbered so as to give the alcohol unit the lowest possible number The alcohol suffix comes after the hydrocarbon suffix minus the "e" : e.g. methane + -ol = methanol propene + -ol = propenol
Although the IUPAC system is preferred, many compounds are still referred by their “common” names. Common Naming System IUPAC NameCommon Name methanolmethyl alcohol or wood alcohol ethanolethyl alcohol Propan-2-olisopropanol
Examples: Draw the following a) 2,3,4-trimethylpentan-1-ol b) 6-ethyl-5,7-dimethyl-4-propyloct-2-yn-4-ol c) 4-methylcyclopent-1-ene-1,2,3-triol
Classifying Alcohols Alcohols are sub classified as primary (1 0 ), secondary (2 0 ), and tertiary (3 0 ) according to the type of carbon to which the –OH group is attached. The OH group is bonded to a carbon that is bonded to only one other carbon atom The OH group is bonded to a carbon that is bonded to only two other carbon atom The OH group is bonded to a carbon that is bonded to only three other carbon atom
Properties of Alcohols Boiling points are much higher than their parent hydrocarbon due to their polarity and hydrogen bonding Alcohols are soluble in polar solvents (such as water) In long-chain alcohols, the hydrocarbon portion of the molecule is nonpolar, making larger alcohols good solvents for nonpolar molecular compounds as well. As a result, a longer alkane will have a higher b.p. than a short alcohol since the longer chain will have more London forces
Reactions of Alcohols Making an Alcohol Alcohols can be prepared by adding water to an alkene (don’t forget about Markovnikov’s rule!)
Reactions of Alcohols (con’t) Elimination of Alcohols Form Alkenes Substitution of Alcohols to Form Alkyl Halides