Ozone Distribution in the Atmosphere STRATOSPHERE TROPOSPHERE 80 60 20 40 km 50 100 150 Ozone Partial Pressure (b) MESOSPHERE *

OZONE Structure of Ozone, O3 O O IN the Stratosphere this allotrope of oxygen, ozone Protects the earth from the sun’s harmful UV radiation. It absorbs it. Can you draw the Lewis Dot Diagram for Ozone?

The Chapman Mechanism + + In the Stratosphere oxygen exists as O2 and O3 and separate single oxygen atom, O. All as it absorbs UV radiation (see left) These 3 forms are in equilibrium with each other O O O O

Ozone, O2 and the Oxygen Atom in Equilibrium 1) Oxygen is homolytically spilt  into free radicals. 2) Ozone gas is the  created. 3) UltraViolet rays as  shown in the picture to the right.

UV light splits Freon into a free radical of Cl● and CF2Cl ● (freon) Freon was thought to be inert CF2Cl2 → CF2Cl. + Cl . (freon) UV light splits Freon into a free radical of Cl● and CF2Cl ●

Ozone Depletion Mechanism Cl· + O3 → ClO· + O2 ClO· + O3 → Cl· + 2 O2 _____________________ 2O3  3 O2

Measurements of Ozone and Reactive Chlorine 1900 1950 1980 300 250 200 150 100 500 1.5 0.5 1.0 Reactive Chlorine Abundance (Parts per Billion) Ozone Abundance (Parts per Billion) THIS FLIGHT WAS THE “SMOKING GUN” *

Fuse School Ozone Destruction #1 https://www.youtube.com/watch?v=J0bx2BuxT-I

Fuse School Ozone Destruction #2 https://www.youtube.com/watch?v=WLqRBc4oxDk

GREENHOUSE EFFECT V OZONE LOSS STUDENTS OFTEN CONFUSE THE GREENHOUSE EFFECT WITH OZONE DEPLETION. THEY ARE VERY DIFFERENT. NEXT IS A FILM CLIP (IF NEEDED ON THE GREENHOUSE EFFECT)

Greenhouse Effect https://www.youtube.com/watch?v=dP-tg4atr5M

BAD OZONE At Ground Level Ozone is toxic When inhaled, ozone can: cause acute respiratory problems aggravate asthma cause inflammation of lung tissue lead to emergency room visits impair the body's immune system 

Naming halogenoalkanes A prefix is added to the name of the alkane. iodine bromine chlorine fluorine halogen prefix five four three two one prefix no. halogen atoms fluoro- – chloro- di- bromo- tri- iodo- tetra- penta- Another prefix is used to indicate how many atoms of each halogen is present. Numbers are used, where necessary, to indicate to which carbon atom(s) each halogen is attached.

As always, keep the numbers as low as possible. 10.1 Naming Alkyl Halides Name is based on longest carbon chain Note: It MUST contain the double or triple bond if present) As always, keep the numbers as low as possible. Halogens have same priority as alkyl groups

Naming with Multiple Halides If more than one of the same kind of halogen is present, use prefix di, tri, tetra If there are several different substituents (halogens or alkyls), number them and list them in alphabetical order

Naming with Multiple Halides If more than one of the same kind of halogen is present, use prefix di, tri, tetra If there are several different substituents (halogens or alkyls) List them in alphabetical order, and keep #’s as low as possible.

What are halogenoalkanes? Halogenoalkanes alkanes with one or more of the hydrogen atoms replaced by a halogen. trichloromethane They can contain more than one type of halogen. For example, CFCs (chlorofluorocarbons) ] Teacher notes Halogenoalkanes are sometimes called haloalkanes.

Physical Properties Alkyl halides are weak polar molecules. No H-bonds

B) propellants for aerosols C) anesthetic USES of Haloalkanes Uses of CFCs CFCs are non-flammable and not very toxic. They therefore had a large number of uses as A) refrigerants B) propellants for aerosols C) anesthetic

USES OF ALKYL HALIDES, OR HALOALKANES

PHYSICAL PROPERTIES Boiling point Increases with molecular size due to increased intermolecular forces bp / °C chloroethane 13 1- chloropropane 47 1-bromopropane 71 (Br has 35 e- to Cl @ 17) Greater branching = lower inter-molecular forces 1-bromobutane CH3CH2CH2CH2Br 101 2-bromobutane CH3CH2CHBrCH3 91 2-bromo -2-methylpropane (CH3)3CBr 73 WHY is this lower? Solubility Haloalkanes are soluble in organic solvents but insoluble in water

Why Branching has lower Boiling Point Branched alkanes have weaker forces because of the smaller area of contact between the molecules. Less energy is needed to overcome the intermolecular force. Linear alkanes can line up more closer and therefore have stronger forces