Chapter 14 Flashcards
(13 cards)
ch14.q2
Draw the structure of 1,2,7,8-TCDD. What is
the full name for this dioxin?
Full name: 1,2,7,8-tetrachlorodibenzo-p-dioxin
Draw: two phenyl groups with oxygen atoms attaching them. Name these spots 10 and 5. Now put four chlorines in at locations 1, 2, 7, 8
For picture see page 628 in the text book.
ch14.q3
What, chemically speaking, was Agent Orange,
and how was it used?
Agent orange (50-50 mixture of 2,4-D and 2,4,5-T). Toxic effects due to dioxin contamination
It was the most effective and widely used herbicide (the forests in Veietnam)
2,4-D = 2,4-dichlophenoxyacetic acid
2,4,5,-T = 2,4,5-trichlophenoxyacetic acid
ch14.q4
Draw the structure of pentachlorophenol. What
is its main use as a compound? What is the main
dioxin congener that it could produce?
- Page 627 in textbook for picture
- Draw: benzene ring and add a chlorine to every bonding site except the one pointing up. On the one pointing up put a hydroxyl group
- Uses:pesticidal applications: herbicide, insecticide, fungicide).
- -> Wood preservatives
Dioxin: Dibenzofurans
ch14.q5
What does PCB stand for? Draw the structural
diagram of the 3,4’,5’-trichloro PCB molecule.
PCB = polychlorinated biphenyls
Draw two biphenyls attached at the middle carbon. This is the spot marked number 1.
when there’s a ‘ the chlorine goes on the left phenyl (counting goes counterclockwise for left benzene ring and clockwise for right benzene ring)
See slide 79 of toxic organic compounds
ch14.q6
What were the main uses for PCBs? What is
meant by an open use?
- Coolants and insulation fluids in electrical transformers and capacitors
- Hydraulic fluids
- Additives in epoxy paints, plasticizers, de-inking fluids for recycled newspaper, non-carbon copy paper
open use = disposal is not controlled
ch14.q7
Draw the structure of a representative
polychlorinated dibenzofuran congener.
slide 70 in toxic organic compounds
ch14.q8
Other than the chlorophenols and PCBs, what
are some of the other sources of dioxins and furans
in the environment? What is currently the largest
anthropogenic source of dioxins?
- Agent orange (50-50 mixture of 2,4-D and 2,4,5-T).
- Municipal incineration emissions, residential wood stoves
- Diesel exhaust emissions
- Metal sintering
- Incomplete combustion in forest fires
ch14.q9
From what medium—air, food, or water—does
most human exposure to dioxin come about? Why
is this so?
Over 90% of human exposure to dioxin is from food sources – especially meat, fish and dairy
Because of biomagnification
ch14.q10
What molecules can be eliminated by a PCB
molecule when it is heated to moderately high
temperatures?
Furans
ch14.q11
Are PCBs acutely toxic to humans? What is
the basis for health concerns about them? Recount
recent evidence that shows PCBs can affect
human development.
- Toxicity depends on congener
- Acute toxicity is generally not a problem, but there are many sub-acute and chronic (long-term) physiological effects,
- Inadvertent PCB poisonings from food
- Effects of in utero exposure
- Thus PCBs appear to interfere with the proper prenatal development of the brain and with the mechanisms that ultimately determine physical size.
ch14.q14
What does TEQ stand for? Why is it used?
TEQ = Toxic Equivalent Factors
The toxic equivalence, or TEQ, of a combination of dioxins and furans is calculating by applying the I-TEF to each concentration of the congener in a sample and summing. Congener concentrations that are below the detection limit are assigned a value of 0 (zero) when calculating TEQ according to the Environment Canada procedure.
ch14.q12
Are all dioxin congeners equally toxic? If not,
what pattern of chlorine substitution leads to the
greatest toxicity? Which is the most toxic dioxin?
- High toxicity
- Toxicity of PCDDs and PCDFs depends on number and positions of the Cl atoms (congeners)
- Most toxic is 2,3,7,8-TCDD
ch14.q13
What is meant by a coplanar PCB?
What structural features give rise to noncoplanarity?
=those in which the two rings are in the same plane.
-most toxic
noncoplanarity = otho postitions
–> least toxic `
