A student was given a sample of an unknown liquid and asked to determine as much as possible about its structure. He was told that the compound contained only carbon, hydrogen, and oxygen, and had only one type of functional group. The student found its boiling point to be 206° C. Using mass spectroscopy, he determined its molecular weight to be 138 g/mol. Finally, he took the infrared spectrum of the compound, which is shown below. From this spectrum, the student quickly reached a conclusion about the functional group. He then turned his attention to the fingerprint region of the compound, which generally has a complicated pattern of peaks that are determined by the structure of the hydrocarbon portion of a molecule. The student decided that the large peak at 750 cm-1 must indicate that this was a disubstituted aromatic compound.Assuming that all of the student's deductions were correct, which of the following could be the structure of the unknown compound?
Answer(s): B
The student theorized that the peak at 750 cm-1 indicates a disubstituted aromatic compound, and since we're told to assume that all of his deductions were correct, this allows us to eliminate choice D, which has only one substituent on the ring. The passage also says that the compound contains only one type of functional group and so choice A, which contains two different functional groups, is also clearly wrong. By the way, neither choice A nor choice D corresponds to the correct molecular weight anyway You are now left with choices B and C, and to decipher between these, you have to look back at the spectrum.If this were an alcohol, as in choice C, the spectrum would contain a broad peak at about 3350 cm-1 to 3250 cm , which is characteristic of a hydroxyl group. This is much like the peak we mentioned for a phenol and for the OH group of a carboxyl group; like those, it's broadened by the fact that it can form hydrogen bonds. This is a very characteristic feature of ANY type of hydroxyl-bearing group, and since it's not here, choice C must be incorrect.
A student was given a sample of an unknown liquid and asked to determine as much as possible about its structure. He was told that the compound contained only carbon, hydrogen, and oxygen, and had only one type of functional group. The student found its boiling point to be 206° C. Using mass spectroscopy, he determined its molecular weight to be 138 g/mol. Finally, he took the infrared spectrum of the compound, which is shown below.From this spectrum, the student quickly reached a conclusion about the functional group. He then turned his attention to the fingerprint region of the compound, which generally has a complicated pattern of peaks that are determined by the structure of the hydrocarbon portion of a molecule. The student decided that the large peak at 750 cm-1 must indicate that this was a disubstituted aromatic compound.The student decides to carry out some simple tests on the compound in order to confirm his identification.Which of the following statements is NOT true?
Answer(s): C
This answer choice is false because neither one will dissolve in aqueous hydrochloric acid. You could use a strong base to distinguish between these two and then the slightly acidic phenol would deprotonate and dissolve as an ion in the aqueous solution. The alcohol, on the other hand, remains uncharged and would not dissolve in the aqueous solution because of its large organic phenyl group. The other three choices are all true statements. For choice A, the benzoic acid will become deprotonated, while the phenol won't. For choice B, the aldehyde will be oxidized, yielding a carboxylic acid, while the ketone won't. Finally, for choice D, sodium hydroxide will hydrolyze the ester-so it will dissolve, while benzyl alcohol will remain insoluble.
Alleles are created when a single gene undergoes several distinct mutations. These alleles may have different dominance relationships with one another; for example, there are three alleles coding for the human blood groups, the IA, IB, and i alleles. Both the IA and IB alleles are dominant to the i allele, but IA and IB are codominant to each other.A multiple-allele system has recently been discovered in the determination of hair coloring in a species of wild rat. The rats are found to have one of three colors: brown, red, or white. Let B = the gene for brown hair; b = the gene for red hair; and w = the gene for white hair. The results from nine experimental crosses are shown below. The males and females in Crosses 1, 2, and 3 are all homozygous for hair color.Based on the experimental results, what is the genotype of the male in Cross 6?
Cross 6 is between a red male and a red female, and their offspring are 100% red. What we need to do is look at the offspring and work backwards to determine the genotypes of their parents. As we've just determined, there are two possible genotypes that correspond to a red phenotype little b, little b and little b, w, since the b allele is dominant to the w allele. With these two genotypes there are three possible types of crosses (you might want to write these down); little b, little b × little b, little b; little b, little b × little b, w; and little b, w × little b, w.Note that we're not taking into account the gender of the parents. By this I mean we're not bothering with the fact that the little b, little b × little b, w cross can occur in two different ways the male can be little b, little b and the female can be little b, w, and vice versA. All of the offspring of Cross 6 are red, therefore, we can eliminate the possibility of a little b, w × little b, w cross since 25% of their offspring would be white. So now we're left with the other two crosses, both of which produce 10% red offspring. If the male is little b, little b, then the female can be either little b, little b or little b, w; and if the male is little b, w then the female must be little b, little b).Hence the male can either be little b, little b or little b, w and the correct answer is choice C.
Alleles are created when a single gene undergoes several distinct mutations. These alleles may have different dominance relationships with one another; for example, there are three alleles coding for the human blood groups, the IA, IB, and i alleles. Both the IA and IB alleles are dominant to the i allele, but IA and IB are codominant to each other.A multiple-allele system has recently been discovered in the determination of hair coloring in a species of wild rat. The rats are found to have one of three colors: brown, red, or white. Let B = the gene for brown hair; b = the gene for red hair; and w = the gene for white hair. The results from nine experimental crosses are shown below. The males and females in Crosses 1, 2, and 3 are all homozygous for hair color.If a large number of brown offspring from Cross 8 are mated with each other, what is the expected percentage of white offspring?
Answer(s): A
Cross 8 is between a brown male and a red female. The fact that 25% of their offspring are white indicates that both parents are heterozygotes, since white fur is a recessive trait. This means that the genotype of the brown male must be big B, w, and the genotype of the red female must be little b, w. Now we need to figure out the genotypes of the brown offspring. A cross between this brown male and red female results in 25% ww offspring, which are white; 25% little b, w, which are red; 25% big B, w, which are brown; and 25% big B, little b, which are brown. So there are two different brown genotypes in the offspring big B, little b and big B, w. If a large number of these brown offspring are mated with each other there are four different crosses possible, and you might want to write them down to avoid confusion; (1) big B, little b × big B, little b; (2) big B, w × big B, w; (3) big B, little b × big B, w; and don't forget (4) big B, w × big B, little b because this is the second way that the third cross can occur. Now we need to figure out what percentage of the offspring produced in these crosses will have white fur. Well, if we work out the Punnett squares, we find that neither the first, the third, nor the fourth crosses yield any white rats. On the other hand, the second cross, big B, w × big B, w, yields 25% white offspring. But you're not through yet; 25% is not your answer. You have to take into account that only one fourth of the total number of possible crosses between two brown rats yields 25% white offspring. Well, one fourth of 25% is 6.25%, which is the correct answer, choice A.
Alleles are created when a single gene undergoes several distinct mutations. These alleles may have different dominance relationships with one another; for example, there are three alleles coding for the human blood groups, the IA, IB, and i alleles. Both the IA and IB alleles are dominant to the i allele, but IA and IB are codominant to each other.A multiple-allele system has recently been discovered in the determination of hair coloring in a species of wild rat. The rats are found to have one of three colors: brown, red, or white. Let B = the gene for brown hair; b = the gene for red hair; and w = the gene for white hair. The results from nine experimental crosses are shown below. The males and females in Crosses 1, 2, and 3 are all homozygous for hair color.Based on the experimental results, what is the genotype of the female in Cross 5?
Answer(s): D
In Cross 5, a brown male is mated with a brown female, and we're told that 100% of their offspring are brown.Since we know that the big B allele is dominant to the little b and w alleles, there are three types of genotypically distinct crosses between two brown parents that result in all brown progeny; again, you might want to write these down to avoid confusion: (1) big B, big B × big B, big B; (2) big B, big B × big B, w; and (3) big B, big B × big B, little b. From this we see that at least one of the parents must be big B, big B. If the female is big B, big B, then the male can be big B, big B; big B, little b; or big B, w. Likewise, if the male is b B, big B, then the female can be big B, big B; big B, little b; or big B, w.
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